Chapter 01

First, know when to get help

Life-threatening hormone emergencies

Call 999 for collapse, a seizure, unconsciousness, severe confusion or a person who is rapidly becoming very unwell. A known hormone condition or steroid medicine can change the emergency treatment needed. Tell the call handler about diagnoses, medicines, emergency cards and any injection already given.

In someone at risk of adrenal crisis, severe weakness, vomiting, abdominal pain, dizziness, collapse or confusion can be a medical emergency. Give prescribed emergency hydrocortisone immediately if trained and available, and call 999. The injection does not replace hospital care. Do not wait for a blood test or for the medicine to work before seeking help.

A sudden severe headache with visual changes, double vision, vomiting or reduced consciousness can signal pituitary apoplexy, especially in someone with a pituitary tumour. Severe low sodium can also cause confusion or seizures. Both require urgent hospital assessment, not a home hormone test.

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Dangerous high or low glucose

Diabetic ketoacidosis can develop quickly and sometimes is the first sign of diabetes. Thirst, passing urine frequently, nausea or vomiting, abdominal pain, deep breathing, fruity-smelling breath and drowsiness are warning signs. Go to A&E or call 999 if DKA is suspected, particularly with confusion, breathing changes or marked deterioration. It can occur even before diabetes has been diagnosed.

A person with diabetes who is conscious and can swallow and whose glucose is below 4 mmol/L should follow the NHS hypo steps: take a fast-acting sugary drink or glucose, recheck after 10 to 15 minutes and repeat if still below 4. Once recovered and above 4, take longer-acting carbohydrate or the next meal. Follow the individual diabetes plan when it gives more specific instructions.

If a person is unconscious or not responding normally, do not put food, drink or tablets in their mouth. Put them in the recovery position if breathing, give prescribed glucagon if available and you know how, and call 999 if glucagon is unavailable, you cannot use it, recovery does not occur within 10 minutes, or alcohol is involved. Stay with them and follow the call handler’s instructions.

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Urgent advice, and how to use this book

A person taking carbimazole who develops fever, sore throat, mouth ulcers or flu-like illness should stop the medicine and seek urgent medical advice immediately for a blood count, following NHS instructions. These can be signs of a rare but serious fall in white blood cells. A very fast heart rate, high temperature, agitation or confusion in someone with an overactive thyroid can indicate thyroid storm and needs emergency care.

Contact a GP urgently or NHS 111 for rapidly worsening symptoms, repeated vomiting, inability to keep essential medication down, or new severe thirst and frequent urination. A known adrenal insufficiency or diabetes sick-day plan may require earlier escalation. If the person is severely unwell, use emergency services rather than waiting for a routine appointment.

Hormone symptoms overlap with many other conditions. This book explains biology, investigation and care; it cannot diagnose an individual or replace medical assessment. Its source-linked research was targeted on 2 November 2026, not systematic or exhaustive. The manuscript has not received independent clinical review or a complete claim-by-claim source audit. Recommendations can change and depend on the person and local services.

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Chapter 02

Hormones: messages between cells

Chemical messengers and their destinations

A hormone is a chemical messenger released by a cell that acts on another cell through a receptor. Endocrine signals travel through the bloodstream; related local signals can act on nearby cells or on the cell that released them. The response depends on the receiving tissue as well as the messenger.

Classic endocrine glands include the pituitary, thyroid, parathyroids, adrenals and pancreatic islets. The brain, digestive tract, kidneys, reproductive organs and other tissues also participate in hormonal communication. These organs interact, so a change in one measurement does not necessarily identify where a problem began.

Hormones help coordinate glucose supply, blood pressure, growth, temperature, reproduction, fluid balance and the response to illness. Their signals vary with meals, sleep, illness and life stage. A snapshot can be useful when collected for a defined question under suitable conditions.

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Receptors and the shape of a response

Peptide hormones such as insulin commonly bind receptors on the cell surface and activate signalling pathways inside the cell. Steroid and thyroid hormones can enter cells and act through receptors that influence gene activity. These are broad patterns, with several interacting pathways.

A tissue may respond differently depending on receptor availability, signalling within the cell and the presence of other hormones. Insulin resistance describes reduced biological response to insulin in relevant tissues; it does not mean that an individual’s entire hormone system has failed.

Some circulating hormones are bound to proteins while a smaller free fraction is available to tissues. Binding proteins and assays affect interpretation of total concentrations. A number needs the right test, units, laboratory method and clinical context before it can explain symptoms.

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Timing, clearance and variation

Hormone secretion may follow daily rhythms or occur in pulses. Cortisol is normally higher around waking and lower late at night, although shift work and sleep timing complicate that pattern. Other hormones vary after a meal, during a menstrual cycle or in response to changing blood chemistry.

Hormones are transported, broken down and cleared at different rates. Illness, kidney or liver disease, prescribed medicines and binding-protein changes can alter what a blood result means. One measurement outside a laboratory interval is a clue, not automatically a diagnosis.

Ask why the test is being done, what time and preparation are needed, and whether a repeat or paired measurement will help. Do not stop a prescribed medicine to prepare for a test unless the clinical team gives a safe, individual plan.

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Chapter 03

Feedback loops and endocrine axes

The hypothalamus and pituitary

The hypothalamus in the brain communicates with the pituitary gland at the base of the brain. The anterior pituitary releases signals such as thyroid-stimulating hormone (TSH) and adrenocorticotropic hormone (ACTH), which act on other glands. The posterior pituitary stores and releases hormones made in the hypothalamus, including arginine vasopressin (AVP).

The thyroid and adrenal cortex then release hormones that act throughout the body. Their output generally feeds back to the hypothalamus and pituitary. This feedback helps maintain a suitable response without keeping every hormone at a fixed number.

The reproductive and growth hormone axes also involve feedback and changing patterns of secretion. A gland, the pituitary, a hormone receptor or an external medicine can each alter the pattern. A clinical question determines which part of an axis needs assessment.

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Primary and central problems

Primary gland failure begins in the target gland. When the thyroid produces too little hormone, TSH often rises because pituitary feedback senses the shortage. In central hypothyroidism the problem is in the pituitary or hypothalamus, so free T4 may be low while TSH is low, normal or otherwise inappropriately modest.

Similarly, primary adrenal insufficiency arises in the adrenal gland; secondary or tertiary insufficiency follows impaired pituitary ACTH or hypothalamic signalling. Primary disease can affect aldosterone as well as cortisol. Aldosterone is usually preserved in central insufficiency because its main regulators are different.

These patterns are not a substitute for clinical diagnosis. Serious illness, medicines and assay interference may change results. If pituitary disease is suspected, clinicians consider the wider set of axes and use specialist advice rather than relying on a single TSH value.

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Dynamic tests and treatment sequence

Some endocrine questions need a stimulation or suppression test: a clinician measures how an axis responds to a controlled signal. A short synacthen test, for example, assesses adrenal cortisol response to a synthetic ACTH-like stimulus. The result depends on indication, assay, preparation and clinical interpretation.

When central hypothyroidism and possible adrenal insufficiency coexist, adrenal function must be assessed and, when needed, glucocorticoid replacement started before thyroid hormone. Starting thyroid replacement without recognising cortisol deficiency can precipitate an adrenal crisis. This is a treatment-sequencing decision for the clinical team.

Tests are not interchangeable simply because each reports a hormone. A well-timed morning cortisol for suspected insufficiency answers a different question from late-night cortisol or a dexamethasone suppression test used for suspected Cushing syndrome.

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Chapter 04

Symptoms, assessment and the first consultation

Patterns are useful, not proof

Fatigue, brain fog, sleep disruption, weight change, palpitations, bowel changes and altered mood can occur in endocrine disease, but each has many other possible causes. An individual can have disabling symptoms even when a first test is normal. A normal result should be explained in relation to the question it was designed to answer.

A cluster and its evolution can help focus assessment. Weight loss, nausea, postural dizziness and salt craving can prompt consideration of adrenal insufficiency; tremor, heat intolerance and palpitations can suggest excess thyroid hormone. Neither combination confirms a diagnosis.

Ask for review of persistent or progressive symptoms and mention changes that are new for you. Consider the full picture, including anaemia, infection, sleep, medications, nutritional problems and other diseases, alongside an endocrine explanation when the history supports it.

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A timeline and medicine history

Record when symptoms began, whether they are constant or episodic, what has changed and how they affect work, sleep and daily life. Note relevant pulse or blood-pressure readings if already available, menstrual changes where relevant, thirst, urination, fainting, changes in skin or vision, and unintended weight change.

Bring prescribed medicines, inhalers, steroid creams or injections, over-the-counter products and supplements, with dates and doses where possible. Previous pituitary surgery, radiotherapy, autoimmune disease, family history and pregnancy can change the interpretation of symptoms and tests.

Symptoms deserve a respectful account even if the first hypothesis changes. Agree which questions the clinician is investigating, when results should arrive and what worsening should trigger urgent reassessment.

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Understanding a result and its limits

A laboratory reference interval describes the range used for a particular method and population; it is not a personal guarantee of health. An abnormal result may need confirmation, and a value within range can still be inappropriate for a paired hormone or a specific clinical setting.

Biotin in hair, skin or nail supplements can interfere with some thyroid and other immunoassays and produce misleading high or low results. Tell the laboratory and clinician about supplements and follow their preparation advice. Antibodies and other assay effects can also cause discordant readings.

When a result does not fit the history, clinicians may repeat it, check sample conditions or use a different method or laboratory. They also consider acute illness, timing and medications. Ask what was measured, the result and units, the laboratory interval, and the planned next step.

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Chapter 05

Pituitary conditions, prolactin and growth hormone

When the pituitary makes too little

Hypopituitarism means deficiency of one or more pituitary hormones. Causes include a pituitary tumour, surgery, radiotherapy, inflammation and other injury. Features depend on which axes are affected and may develop gradually; headache or visual change can also arise from a mass pressing on nearby structures.

The team may use paired pituitary and target-gland hormones, dynamic tests and pituitary MRI when indicated. A scan and the hormone pattern answer different questions. Some pituitary findings are incidental and do not automatically explain every symptom.

Treatment replaces deficient hormones when appropriate and addresses the cause. Follow-up includes checking for too little or too much replacement, visual problems and changes in other axes. A sudden severe headache with visual loss or collapse is an emergency rather than a routine review.

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Prolactin: one result, several explanations

Prolactin supports milk production after childbirth. Raised prolactin can affect reproductive hormone signalling and may be associated with milk discharge, menstrual disturbance, reduced libido or fertility problems. Symptoms vary and are not specific to a prolactin disorder.

Pregnancy, breastfeeding, some medicines, underactive thyroid and pituitary tumours called prolactinomas are among the possible explanations. A modest elevation may need a repeat under suitable conditions and review of medicines and other causes. Some laboratories check macroprolactin, a form that can affect the result while having less biological activity.

The size of a prolactinoma, symptoms, fertility plans and other findings influence treatment. Medicines that reduce prolactin can be effective for many patients; specialist follow-up considers both hormone levels and tumour size. Do not stop an antipsychotic or other essential medicine without the prescriber’s advice.

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Growth hormone and acromegaly

Growth hormone acts partly through insulin-like growth factor 1, or IGF-1. In adults, excess growth hormone usually results from a pituitary tumour and can cause acromegaly. Changes may be gradual: enlarging hands or feet, altered facial features, sweating, headaches and joint symptoms can be missed for years.

A specialist can measure IGF-1 and arrange further testing, including assessment of growth hormone suppression after glucose, and imaging where appropriate. A random growth hormone result is difficult to interpret because secretion is pulsatile. Associated effects can involve blood pressure, diabetes, sleep and heart health.

Treatment options include surgery, medicines and sometimes radiotherapy, selected with specialist input. Growth hormone deficiency is a different condition and is assessed in the appropriate pituitary context. Neither fatigue nor a single unscheduled growth hormone result establishes deficiency.

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Chapter 06

Stress physiology and the cortisol rhythm

The stress response has a biological purpose

When the brain perceives a challenge, the sympathetic nervous system and hypothalamic-pituitary-adrenal, or HPA, axis help coordinate a response. The hypothalamus releases signals that promote ACTH release; ACTH stimulates cortisol production by the adrenal cortex. Adrenaline and related signals contribute to a faster response.

Cortisol influences fuel availability, immune activity, blood pressure and many other processes. It is also present during ordinary daily life and normally follows a daily rhythm. An acute response to infection, injury or emotional stress is not the same thing as a diagnosis of an endocrine disease.

Stress can influence sleep, concentration, pain and symptom burden. Long-term stress can coexist with thyroid disease, diabetes or another illness. Explaining a physiological pathway should not be used to dismiss a person’s symptoms or end an indicated medical assessment.

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A rhythm is not a single optimum value

Cortisol changes across the day and responds to sleep, acute illness, medicines and binding proteins. A result needs its collection time and reason for testing. A late-night sample can be part of an assessment for excess cortisol, while a morning blood sample is used in a different pathway for possible deficiency.

Blood, saliva and urine do not measure interchangeable quantities under every circumstance. Laboratories and specialist teams specify preparation, test method and interpretation. A commercially presented daily curve should not be treated as proof of a particular disease without validated clinical interpretation.

If a result and symptoms conflict, ask whether the collection time, relevant medication or test method could have influenced the result. Retesting or referral may be appropriate, but a single number cannot determine the right treatment for every person.

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Distress, fatigue and the adrenal fatigue label

People with prolonged exhaustion and poor sleep deserve an assessment that takes their experience seriously. “Adrenal fatigue” is not a recognised endocrine diagnosis, and the Endocrine Society says there is no scientific proof that the adrenal glands become exhausted by everyday stress in the way this label implies.

This differs from adrenal insufficiency, a potentially life-threatening deficiency with recognised causes and testing pathways. A reassuring cortisol result in the appropriate setting does not explain away fatigue; it helps direct attention to other possible causes and supportive care.

Do not take steroid-containing or unverified “adrenal support” products to correct a presumed deficiency. If you are already using them, tell a clinician what you take and agree how to review it safely. Stopping genuine glucocorticoid exposure abruptly can itself be dangerous.

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Chapter 07

Adrenal insufficiency, steroid exposure and crisis

Recognising insufficient cortisol

Adrenal insufficiency is inadequate production of cortisol, with different underlying causes. In primary adrenal insufficiency, also called Addison’s disease, the adrenal glands themselves are affected and aldosterone deficiency may occur. Secondary and tertiary forms arise from insufficient pituitary or hypothalamic stimulation, including after glucocorticoid exposure.

NICE lists persistent unexplained weight loss, nausea, vomiting, loss of appetite, postural dizziness, salt craving, weakness, lethargy and low sodium among features that can prompt consideration. Darkening of skin or scars can occur in primary disease, but may be harder to see on brown or black skin; its absence does not exclude the diagnosis.

Risk is higher in some people with autoimmune conditions, pituitary disease or recent glucocorticoid withdrawal. Symptoms are not specific, so the clinical team considers the whole picture. Acute deterioration or suspected crisis requires emergency treatment rather than waiting for outpatient tests.

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Morning cortisol in the NICE pathway

For suspected adrenal insufficiency in people aged one year and over, NICE recommends an 8 to 9 am serum cortisol in the appropriate pathway. For adults aged 16 and over, below 150 nmol/L suggests possible insufficiency and warrants endocrinology referral; 150 to 300 is uncertain, with repeat testing and advice if it remains in that interval; above 300 makes insufficiency very unlikely.

These cut-offs apply to modern immunoassays and the specified collection time, not every laboratory method, random sample or clinical scenario. A baby under one needs a different approach. Recent injections, exogenous glucocorticoids, oral oestrogen and acute illness can affect testing or interpretation; NICE provides specific preparation and exceptions.

NICE says not to test for adrenal insufficiency in people taking oral glucocorticoids at physiological equivalent doses or above. The clinician chooses the appropriate withdrawal or testing pathway and whether a specialist stimulation test is needed. Never delay emergency treatment for a test result.

Sources for this section

NICE NG243: Adrenal insufficiency, identification and management (https://www.nice.org.uk/guidance/ng243/chapter/recommendations)

Replacement, sick days and preventing crisis

Glucocorticoid replacement is essential for confirmed adrenal insufficiency. Some people with primary insufficiency also need mineralocorticoid replacement. The team adjusts treatment to the condition and individual response; too little and too much replacement can both cause problems.

NICE recommends education on a steroid emergency card, medical identification, an adequate medicine supply, an individual sick-day plan and emergency injectable glucocorticoids. Illness, vomiting, surgery or injury can require additional treatment. Ask your team exactly when and how to use the plan, and ensure family or carers know where it is.

If adrenal crisis is suspected, give the prescribed emergency injection if available and trained, call 999, and tell emergency staff about adrenal insufficiency or steroid use. Hospital treatment is still required. Do not abruptly stop prescribed replacement or long-term steroid treatment without the treating team’s advice.

Sources for this section

NICE NG243: Adrenal insufficiency, identification and management (https://www.nice.org.uk/guidance/ng243/chapter/recommendations)

Chapter 08

Cortisol excess, aldosterone and adrenal tumours

Cushing syndrome and careful testing

Cushing syndrome results from sustained exposure to excess glucocorticoid. Prescribed steroids are an important cause and the full medication history must be reviewed before testing for endogenous overproduction. Features can include progressive central weight gain, easy bruising, muscle weakness and broad purple stretch marks, though no single feature proves the diagnosis.

The Endocrine Society guideline recommends directed testing in people with appropriate features after excluding steroid exposure. Depending on the person and specialist advice, first-line options include late-night salivary cortisol, 24-hour urinary free cortisol or a low-dose dexamethasone suppression test. A random cortisol is not a recommended screening test for Cushing syndrome.

Abnormal results can have other explanations, and cyclic disease or collection errors can complicate interpretation. Follow-up tests and assessment distinguish pituitary, adrenal and other causes. The guideline is international; local NHS endocrinology pathways and laboratory methods determine how it is applied.

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Aldosterone, renin and high blood pressure

Aldosterone promotes sodium retention and potassium excretion by the kidney and contributes to blood-pressure regulation. In primary aldosteronism the adrenal gland produces too much aldosterone relative to the usual renin signal. Blood pressure can be difficult to control; low potassium can occur, but many affected people have potassium within the reference range.

Screening uses aldosterone and renin, often expressed as a ratio, with potassium measured to aid interpretation. Sampling conditions, sodium intake, low potassium and blood-pressure medicines can affect the result. A positive screen is not by itself the final diagnosis or proof that one adrenal gland is responsible.

The 2025 Endocrine Society guideline conditionally suggests screening all people with hypertension, subject to resources and local context. This international recommendation is not automatically NHS policy. Do not stop blood-pressure treatment or change salt intake independently to prepare for a test; discuss the safe local pathway with the clinician.

Sources for this section

Endocrine Society: Primary aldosteronism guideline, 2025 (https://www.endocrine.org/clinical-practice-guidelines/primary-aldosteronism-2)

Phaeochromocytoma and incidental findings

A phaeochromocytoma is a rare tumour, usually in an adrenal gland, that can release excess adrenaline-like hormones. Episodes may include headache, sweating, palpitations and high blood pressure, sometimes with a pale appearance or anxiety-like sensations. These symptoms have many causes; they warrant assessment rather than an assumption of a rare tumour.

Clinicians may use blood or urine measurements of metanephrines and imaging when the history raises suspicion. Sampling and medicines can affect results. Treatment and preparation for surgery require specialist care because changes in hormone release can have serious cardiovascular effects.

An adrenal lump found on a scan may be unrelated to the reason for imaging. The team assesses its appearance and whether it produces hormones before deciding on follow-up or treatment. A scan alone cannot show whether aldosterone, cortisol or adrenaline production is abnormal.

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Chapter 09

Insulin, glucagon and the supply of fuel

The pancreatic islets

Within the pancreas, clusters of cells called islets release hormones into the blood. Beta cells produce insulin; alpha cells produce glucagon. Other islet cells release signals, including somatostatin, that participate in local regulation. This hormone function is distinct from the pancreas producing digestive enzymes.

After a meal, rising glucose and other signals stimulate insulin secretion. Insulin helps muscle and fat take up glucose and helps the liver store and manage fuel. Glucagon helps the liver release glucose, especially when blood glucose is falling or a person has not recently eaten.

The response depends on communication between the pancreas, liver, muscle, fat, gut and brain. Glucose is dynamic. A rise after eating is expected; its size and duration depend on the meal, activity, medicines and the person’s physiology.

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Resistance and the beta-cell response

Insulin resistance means that a given amount of insulin has less effect in relevant tissues. The pancreas may compensate by releasing more insulin. Type 2 diabetes develops when insulin secretion is insufficient for the body’s needs in the context of insulin resistance and other processes.

Insulin resistance is influenced by multiple factors, including genetics and health conditions. It is not a moral judgement or a result that can be reliably inferred from appearance. Not every person with insulin resistance develops diabetes, and not every high glucose reading establishes its cause.

Treatments target different parts of the system: some improve insulin sensitivity, some increase glucose loss through the kidneys, and others replace insulin or affect gut-hormone pathways. Choice depends on the diagnosis, other conditions, preferences and safety.

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The gut and the counter-regulatory response

Gut hormones called incretins help coordinate the insulin response to a meal. GLP-1 and GIP are examples. Their effects are glucose-dependent and interact with other signals; this physiology is one basis for medicines used in diabetes and, in specific circumstances, weight management.

When glucose falls, the body normally reduces insulin release and recruits counter-regulatory signals including glucagon and adrenaline. Shaking, sweating and palpitations can accompany this response, while confusion and impaired consciousness can occur when the brain is short of glucose.

Responses can be altered by diabetes, recurrent hypoglycaemia or medicines. Symptoms and a measured glucose value need to be considered together. A symptom after a meal alone cannot establish a glucose disorder or determine the right treatment.

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Chapter 10

Diabetes: types, diagnosis and ongoing care

Different mechanisms can produce high glucose

Diabetes means persistently elevated blood glucose caused by insufficient effective insulin action. Type 1 diabetes usually involves immune-mediated loss of insulin-producing cells and requires insulin. Type 2 involves a combination of reduced insulin sensitivity and inadequate insulin secretion for the person’s needs.

Other forms include diabetes associated with pancreatic disease, medicines or inherited conditions, and diabetes first recognised in pregnancy. A classification may be revised as new evidence emerges. NICE says age and BMI alone must not be used to diagnose or exclude type 1 diabetes in adults.

Thirst, frequent urination, fatigue and unintended weight loss can occur with hyperglycaemia. Rapid deterioration, vomiting, deep breathing or drowsiness can indicate ketoacidosis and requires emergency care. A person with newly suspected type 1 diabetes needs prompt clinical assessment, not a delayed routine test.

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Glucose, HbA1c and classifying diabetes

A laboratory glucose test measures the concentration at the time of sampling. HbA1c reflects the proportion of glycated haemoglobin and is used to assess longer-term glucose exposure. It can help diagnose or monitor diabetes in suitable circumstances, but it does not show every high or low glucose episode.

HbA1c can be misleading when red-cell survival or haemoglobin is altered, including some anaemias and haemoglobin variants; rapidly developing symptoms and other circumstances may require glucose-based assessment instead. Ask the clinician which test is appropriate and whether a result needs confirmation.

For adults initially diagnosed with type 1 diabetes, NICE recommends diabetes-specific autoantibody testing. It does not routinely recommend C-peptide at diagnosis, but non-fasting C-peptide paired with glucose can help if antibodies are negative and classification remains uncertain; it can also help revisit a doubtful diagnosis later. Treatment must not wait for antibody results when insulin is urgently needed.

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Treatment is more than a glucose number

People with type 1 diabetes need insulin and education in its use, glucose monitoring and recognising emergencies. Depending on eligibility and the care plan, monitoring technology or an insulin pump may help. The diabetes team supports individual targets and reviews risks of both high and low glucose.

For adults with type 2 diabetes and no relevant comorbidities, the 2026 NICE update recommends offering modified-release metformin and an SGLT-2 inhibitor as initial medicines; if metformin is contraindicated or not tolerated, it recommends an SGLT-2 inhibitor alone. Other clinical circumstances have different recommendations. Discuss kidney function, side effects, contraindications and individual suitability.

The aim includes cardiovascular and kidney health as well as glucose management. SGLT-2 inhibitors have potential benefits but can increase genital infection and volume-depletion risks and rarely are associated with ketoacidosis, including when glucose is not markedly high. Ask for a medicine-specific sick-day plan and do not change treatment without advice.

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Chapter 11

Low blood glucose: recognising and investigating a hypo

Why glucose can fall

Low glucose is most common in people with diabetes who use insulin or medicines such as gliclazide. Delayed meals, exercise, alcohol and a mismatch between medicine and food can contribute. Symptoms include hunger, sweating, shaking, palpitations, irritability and confusion; severe episodes may cause seizures or unconsciousness.

NHS advice usually describes a hypo as glucose below 4 mmol/L and recommends prompt treatment for people with diabetes who have symptoms or a reading below that level. Some people notice fewer warning signs after repeated episodes. Frequent, severe or nighttime hypos need review with the diabetes team.

Low glucose without diabetes is uncommon. Symptoms that resemble a hypo can also have other explanations. A clinician will consider medicines, nutrition, illness and other causes rather than diagnosing a pancreatic tumour or hormone deficiency from symptoms alone.

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What to do when a person can swallow safely

For someone with diabetes who is awake and can swallow, NHS guidance advises a quick-acting sugar such as a small glass of fruit juice or sugary, not diet, fizzy drink, glucose tablets or glucose gel. If a meter is available, check the reading; do not delay treatment of symptoms while looking for equipment.

Recheck after 10 to 15 minutes. If glucose is still below 4 mmol/L, take more quick-acting sugar and check again after 10 minutes. Once symptoms improve and the level is above 4, have longer-acting carbohydrate such as a sandwich or the next meal if due.

Follow the individual plan, including any instructions for children or people using devices. Do not drive during or immediately after a hypo. NHS guidance advises waiting at least 45 minutes after glucose returns to normal; check current DVLA rules and discuss recurrent episodes with the diabetes team.

Sources for this section

NHS: Low blood sugar (hypoglycaemia) (https://www.nhs.uk/conditions/low-blood-sugar-hypoglycaemia/)

Severe episodes and assessment without diabetes

Never give food or drink to a person who is unconscious or unable to swallow safely. Use the recovery position if breathing and give prescribed glucagon if available and you know how. Call 999 if it is unavailable, you cannot use it, the person has not recovered within 10 minutes or alcohol is involved.

In a person without diabetes, an assessment may seek evidence that symptoms occur with low measured plasma glucose and improve when glucose is raised. This relationship, often called Whipple’s triad, helps distinguish a true hypoglycaemic disorder from symptoms with another cause.

The test and timing depend on whether episodes occur fasting or after meals. A supervised fast or other specialist investigation is not a home experiment. Do not deliberately provoke symptoms, fast for a prolonged period or interpret a single consumer sensor dip as a diagnosis.

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Chapter 12

Thyroid physiology, testing and underactivity

The thyroid and its feedback loop

The thyroid gland in the neck produces thyroxine, or T4, and triiodothyronine, or T3. Thyroid hormones affect energy use and many tissues, including the heart, nervous system and gut. The pituitary releases TSH to stimulate the thyroid, with feedback from circulating thyroid hormones.

The thyroid produces mainly T4; tissues convert some T4 to the more active T3. Much hormone is protein-bound, while free hormone measurements estimate the unbound fraction. The right interpretation depends on the clinical question and the laboratory method.

Thyroid symptoms overlap with other conditions. NICE cautions that one symptom alone may not indicate thyroid disease and generally advises against thyroid testing during acute illness unless the illness is suspected to be due to thyroid dysfunction.

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TSH, free T4 and the pituitary exception

For adults without suspected pituitary disease, NICE recommends considering TSH first, with free T4 measured on the same sample if TSH is high and free T4 plus free T3 if TSH is low. When secondary thyroid dysfunction is suspected, it recommends considering TSH and free T4 together.

High TSH with low free T4 is a common pattern in primary hypothyroidism. A low free T4 with TSH that is not appropriately raised can suggest central hypothyroidism. Assay effects, medication and acute illness can complicate the pattern, so a clinician interprets it in context.

Biotin supplements can distort some immunoassay results. Tell the clinician what you take. NICE advises repeat thyroid testing if symptoms worsen or new ones develop, but generally no sooner than six weeks after the most recent test. A repeat plan should be individualised.

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Underactive thyroid and levothyroxine

Underactive thyroid can cause tiredness, cold intolerance, constipation, weight change, dry skin and difficulty concentrating. Autoimmune thyroid disease is one cause; thyroid surgery, radioactive iodine and certain medicines can also be relevant. These symptoms do not establish hypothyroidism without suitable tests.

NICE recommends levothyroxine as first-line treatment for primary hypothyroidism. The starting dose and adjustment depend on age, cardiovascular history and other circumstances. Take it as instructed, and tell the prescriber about medicines or supplements that could affect absorption; treatment is monitored rather than adjusted from day-to-day feelings alone.

For persistent symptoms NICE supports reassessment and considering free T4 alongside TSH, while avoiding doses that suppress TSH or cause thyrotoxicosis. It does not routinely recommend liothyronine or natural thyroid extract for primary hypothyroidism because evidence of additional benefit is insufficient and long-term harms remain uncertain. Continuing symptoms deserve a wider assessment.

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Chapter 13

Overactive thyroid and thyroid enlargement

Different paths to excess thyroid hormone

Thyrotoxicosis describes excess circulating thyroid hormone. It can arise from increased hormone production, as in Graves’ disease or overactive nodules, or from release of stored hormone during thyroiditis. These causes may need different treatment; an abnormal test does not by itself show which one is present.

Symptoms can include heat intolerance, tremor, palpitations, anxiety, weight loss, frequent bowel motions and disturbed sleep. The pattern varies. Untreated excess thyroid hormone can affect the heart and bone, so ongoing symptoms and abnormal tests deserve a treatment and monitoring plan.

Tests may include TSH, free hormones and, when appropriate, antibodies, imaging or specialist assessment. Graves’ disease can also cause thyroid eye disease. New eye pain, double vision or changes in sight should be reported promptly.

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Treatment choices and urgent medicine effects

Antithyroid medicines, radioactive iodine and surgery are options for some forms of overactive thyroid. Choice depends on the cause, severity, thyroid size, eye disease, age, pregnancy plans and preferences. Some treatments can lead to an underactive thyroid requiring replacement.

Carbimazole can rarely cause a dangerous reduction in white blood cells. NHS advice is to stop it and seek urgent medical advice immediately if fever, sore throat, mouth ulcers or flu-like symptoms develop. Report yellowing of the skin or eyes and other serious side effects promptly as directed by the medicine guidance.

Thyroid storm is rare and life-threatening. High temperature, a rapid heartbeat, agitation or confusion, especially in someone with known hyperthyroidism, requires emergency help. Pregnancy and planning pregnancy require early discussion because disease and treatment both affect the care plan.

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A lump or enlarged thyroid

A goitre is an enlarged thyroid; nodules are areas of growth within it. NICE notes that goitres and nodules are common and usually not cancerous. Their presence does not establish whether thyroid hormone production is high, low or normal.

Evaluation depends on the lump, examination, thyroid blood tests and whether imaging or a specialist assessment is indicated. A scan can describe structure but does not by itself answer every question about hormone production or exclude all disease.

Tell a clinician about rapid growth, hoarseness, difficulty swallowing or shortness of breath. These are important symptoms even if a previous test was reassuring. Agree how results and any planned follow-up will be communicated.

Sources for this section

NICE NG145: Thyroid disease, assessment and management (https://www.nice.org.uk/guidance/ng145/chapter/recommendations)

Chapter 14

Parathyroid hormone, calcium and phosphate

Keeping calcium available

The parathyroid glands, usually four small glands near the thyroid, release parathyroid hormone (PTH). Calcium is needed for nerve and muscle function as well as bone structure. PTH helps regulate blood calcium through effects on bone and kidney and by promoting activation of vitamin D.

Active vitamin D helps the gut absorb calcium and phosphate. The kidneys, intestine and bone participate in a linked system that balances supply and losses. Kidney function and vitamin D status can therefore change both calcium and PTH interpretation.

PTH should be interpreted alongside a calcium measurement taken at the same time. A PTH result within the laboratory interval may still be inappropriately high when calcium is elevated, because normal feedback should suppress PTH in that setting.

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Primary hyperparathyroidism: the NICE pathway

Primary hyperparathyroidism is excess PTH production arising from the parathyroid glands. It can be discovered on a blood test or investigated because of thirst, frequent urination, constipation, kidney stones, osteoporosis or fragility fracture. Symptoms are not specific and can have other explanations.

NICE recommends repeating albumin-adjusted calcium at least once if it is 2.6 mmol/L or above, or 2.5 mmol/L or above with features of primary hyperparathyroidism. It recommends measuring PTH with concurrent adjusted calcium after the specified repeated elevations. These are pathway thresholds, not universal targets for every calcium result.

Specialist assessment may include vitamin D, kidney function, urine calcium to help distinguish familial hypocalciuric hypercalcaemia, a DXA scan and renal imaging. In confirmed disease, NICE recommends surgical referral for symptoms of hypercalcaemia, end-organ disease, or adjusted calcium of at least 2.85 mmol/L; it also considers referral in other cases.

Sources for this section

NICE NG132: Primary hyperparathyroidism (https://www.nice.org.uk/guidance/ng132/chapter/recommendations)

Calcium emergencies and low calcium

High calcium can cause thirst, frequent urination, constipation, weakness and confusion. Severe elevation can cause dehydration and serious illness. The urgency depends on symptoms, level and rate of change; marked confusion, collapse or rapid deterioration warrants emergency care rather than waiting for a routine appointment.

Low calcium can cause tingling around the mouth or in the hands and feet, muscle cramps or spasms. Severe low calcium may cause seizures, heart rhythm problems or breathing difficulty and requires urgent hospital treatment. Causes include parathyroid disease, surgery, vitamin D problems and other conditions.

The clinical team interprets calcium with the history and relevant blood tests, including magnesium and kidney function where indicated. Do not attempt to correct a severe abnormal result with large supplement doses at home. Ask what the result means and when it will be checked again.

Sources for this section

Chapter 15

Bone health and endocrine fracture risk

Bone is living tissue

Bone is continually remodelled: cells remove old bone and other cells lay down new material. Calcium and phosphate form part of its mineral structure, but bone strength also depends on its architecture and quality. Hormones influence this process across life.

Excess thyroid hormone, hyperparathyroidism, Cushing disease and low sex hormone states can affect fracture risk. Diabetes and some medicines are also relevant. Having one risk factor does not mean a fracture is inevitable, and a normal blood calcium result does not measure bone strength.

A fragility fracture is a break after a relatively minor injury, such as a fall from standing height or less. A previous fracture can be a major warning about future risk and is worth discussing even if it has healed.

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Who should have risk assessed?

The 2026 NICE osteoporosis guideline recommends assessing fragility fracture risk in people aged 50 and over and women who have experienced menopause when they have a previous fragility fracture or current or frequent systemic glucocorticoid use at the specified exposure. It lists other factors for which assessment should be considered.

NICE gives the example of prednisolone at 5 mg daily or equivalent for more than three months, or intermittent higher doses, while excluding replacement doses for adrenal insufficiency from that example. Younger people with particular fracture histories or major risk factors have their own assessment recommendations.

Risk assessment considers more than a scan: age, fracture history, falls, medication, weight and other conditions all matter. A DXA scan can measure bone mineral density when appropriate, but the decision to investigate and treat depends on the whole clinical picture.

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A plan after assessment

Ask which risk factors are present, whether a DXA scan or further investigation is useful, and whether an endocrine or other underlying condition needs treatment. Vertebral fractures can be missed, so report unexplained height loss, a change in posture or persistent back pain to a clinician.

A plan can include treatment of the underlying disorder, prevention of falls and bone-protective medicines when indicated. Adequate nutrition and activity appropriate to the individual matter, but they do not replace assessment or prescribed treatment after a fragility fracture.

If long-term steroids are needed for another condition, discuss fracture risk and protection with the prescriber. Do not stop an essential glucocorticoid abruptly, including replacement for adrenal insufficiency.

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Chapter 16

Thirst, vasopressin and sodium balance

How water balance is controlled

Arginine vasopressin, also called antidiuretic hormone, is made in the hypothalamus and released through the posterior pituitary. It acts on the kidneys to conserve water. Thirst and the kidneys’ response work alongside it to help regulate the concentration of blood.

When water is retained out of proportion to sodium, blood sodium concentration can fall; when water is lost without enough replacement, it can rise. A sodium result reflects the balance of water and solute, not simply the amount of salt eaten.

Thirst and frequent urination have several possible causes, including high blood glucose, medicines and kidney problems. Persistent or marked symptoms deserve assessment. Rapid deterioration, confusion, seizure or collapse requires emergency care.

Sources for this section

AVP deficiency and resistance

Diabetes insipidus, a name now also described using AVP deficiency or resistance, is different from diabetes mellitus. In AVP deficiency the body does not release enough vasopressin; in AVP resistance the kidneys do not respond adequately. Both can lead to large volumes of dilute urine and intense thirst.

Assessment may involve blood and urine measurements and specialist-supervised testing. The team also considers other explanations for excess drinking or urination. Do not attempt a water-deprivation test at home: restricting water in someone unable to conserve it can be dangerous.

Desmopressin replaces the missing antidiuretic effect in AVP deficiency. NHS England warns that omitted or delayed desmopressin can cause severe dehydration and death in patients who depend on it. Tell hospital staff about the diagnosis and usual schedule, and ask how treatment will continue if you cannot take the usual form.

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Low sodium and desmopressin safety

Hyponatraemia means a low sodium concentration in the blood. It has several causes, including illness, medicines and inappropriate antidiuretic activity. Nausea, headache and tiredness can occur; severe symptoms include confusion, seizures and reduced consciousness. Severity depends on the clinical situation as well as the number.

Too much desmopressin or excessive fluid intake while it is acting can cause water retention and low sodium. Follow the individual team’s instructions about dosing, drinking and monitoring. Seek prompt advice for headache, nausea, unexplained weight gain or other concerning symptoms; severe confusion or seizures need emergency care.

Severe symptomatic hyponatraemia requires monitored hospital treatment. Correcting sodium too rapidly can itself cause neurological injury. Do not try to correct a sodium result at home by changing salt, water or desmopressin doses without a clinician-directed plan.

Sources for this section

Chapter 17

Medicines, monitoring and shared decisions

What medicines can change

Hormone treatments can replace a deficiency, block excessive production or change the effect of a signal. Other medicines, including steroids and some diabetes drugs, can influence endocrine function or test results. Record the name, dose, route and start date, including creams, injections, inhalers and supplements.

Glucocorticoids can suppress the HPA axis even when given by routes other than tablets. The chance and duration depend on the preparation, exposure and person. NICE highlights risk after glucocorticoid withdrawal and provides a clinician-led approach to tapering and testing.

Biotin may interfere with immunoassays, oral oestrogen can alter cortisol-binding proteins, and medicines can alter aldosterone-renin testing. The relevant laboratory or clinician should give preparation instructions. Never stop essential treatment, contraception or steroid replacement on your own to make a test easier.

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Questions to take to an appointment

Ask: What is the leading explanation? Which alternative is important not to miss? What test is being ordered, under what conditions, and what result would change the plan? If a test is not indicated, ask what signs or changes would make it useful later.

For a treatment, ask about expected benefit, likely adverse effects, interactions, monitoring and when the team will review whether it is helping. If more than one option is reasonable, discuss the trade-offs in relation to work, travel, pregnancy plans, costs and accessibility.

Ask for the actual result, units and laboratory interval, and who will contact you. Agree a review date and what to do if symptoms continue or worsen. A second discussion can be useful when the result is technically normal but the original problem remains unresolved.

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Coordinating care and emergency plans

If more than one team prescribes or monitors treatment, ask who is responsible for repeat prescriptions, blood tests and communicating changes. Bring an up-to-date list when attending a new service or hospital and explain any condition for which a missed dose can be dangerous.

A steroid emergency card and individual sick-day instructions matter for adrenal insufficiency; a desmopressin plan matters for AVP deficiency; diabetes care can require a hypo, ketone and sick-day plan. Ask how to obtain supplies and what to do during vomiting, an operation, travel or an admission.

Share relevant instructions with a trusted person if you wish, including where emergency medication is kept and how to use it. If an emergency occurs, use the action plan and emergency services. A planned review is also the place to raise persistent symptoms, uncertainty about a diagnosis or difficulties following treatment.

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Chapter 18

Reproductive hormones across the life course

The brain, pituitary and reproductive organs

The hypothalamus releases gonadotrophin-releasing hormone in pulses. This stimulates the pituitary to release luteinising hormone (LH) and follicle-stimulating hormone (FSH). These travel in blood to the ovaries or testes, participating in sex hormone production and the processes supporting egg or sperm development.

Oestradiol, progesterone, testosterone and other signals feed back to the brain and pituitary. Feedback changes with context: in an ovulatory cycle, sustained high oestradiol contributes to a mid-cycle LH surge, while other stages involve different feedback. One hormone number cannot describe the entire system.

People have sex hormones regardless of gender, and concentrations, anatomy and treatment histories vary. Effects depend on the tissue receiving a signal, receptors, binding proteins and timing. A laboratory result needs the right context before interpretation.

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Puberty is a transition, not a single event

During puberty, increased activity in reproductive signalling contributes to changes in growth, body composition, skin, body hair, breasts or genital development. Ovarian activity can lead to periods; testicular activity supports testosterone production and sperm development. Timing and sequence vary. Physical changes can have emotional and social consequences.

Early cycles can be irregular as the ovulatory system matures. Irregularity in an adolescent should still be interpreted against time since the first period and the symptom pattern. The international PCOS guideline uses specific adolescent criteria rather than assuming every irregular cycle is PCOS.

A young person with unexpectedly early or delayed changes, severe distress, or a change in growth should be able to discuss this confidentially with a GP or appropriate paediatric service. Differences in sex development have several causes and individual needs; neither identity nor a single visible feature identifies the whole biology.

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A changing system needs a changing question

Reproductive hormones change with age, the menstrual cycle, pregnancy, illness, medication and some gender-affirming treatments. Removal of gonads or medical treatment affecting them can alter hormone production at any age. These experiences cannot be inferred from how someone looks.

A useful history asks what changed, when it began, whether it is cyclical, what medicines or treatments are used and which outcomes matter. It also asks about relevant anatomy and reproductive goals without assuming that everyone menstruates, wants pregnancy or identifies with the same terms.

Hormone-related symptoms can overlap with infection, anaemia, mental health conditions, medication effects and many other problems. Understanding a possible pathway helps form a question; it does not replace assessment of the whole person.

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Chapter 19

The menstrual cycle in detail

Follicular phase and ovulation

A cycle is counted from the first day of menstrual bleeding to the day before the next period. Early in the cycle, FSH supports growth of ovarian follicles, structures containing immature eggs. Developing follicles produce oestradiol, which helps the uterine lining build after the preceding bleed. A dominant follicle usually becomes the one that ovulates.

As oestradiol rises sufficiently and remains high, feedback changes and an LH surge helps trigger ovulation. Timing is variable: a 28-day example is a teaching model, not a required pattern. Stress, illness, age, energy availability, medications and individual variation can alter timing or prevent ovulation.

Cervical mucus changes around the fertile window and ovulation-prediction kits detect a urinary LH rise, but neither guarantees fertilisation or a pregnancy. Discuss a concern about irregular or absent periods with a clinician rather than relying solely on an app's predicted day.

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The luteal phase and menstruation

After ovulation, the follicle becomes the corpus luteum and produces progesterone along with oestradiol. Progesterone changes the uterine lining in preparation for possible implantation. If pregnancy does not occur, the corpus luteum regresses, hormone concentrations fall and the lining is shed during menstruation.

An ovulatory cycle is not established by bleeding alone. Bleeding may occur when ovulation has not taken place, and hormonal contraception changes both bleeding and hormone patterns. A progesterone blood test can help assess ovulation when timed appropriately, but one value is a snapshot and requires interpretation within the question being asked.

For fertility investigation NICE describes mid-luteal progesterone, day 21 in a 28-day cycle. For longer irregular cycles, testing may need to be later and repeated. A fixed day-21 test can mislead when the cycle is not 28 days; arrange the timing with the requesting clinician.

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Tracking symptoms without drawing premature conclusions

A short cycle diary can record the first day and duration of bleeding, approximate flow, pain, mood, sleep and medication. Note impacts such as missing work, school or usual activities. A repeated pattern can help a clinician distinguish a premenstrual pattern from symptoms that persist throughout the cycle.

Heavy bleeding, severe pain, bleeding between periods or pain with sex has several possible explanations. A diary does not diagnose low progesterone, endometriosis or an ovarian condition. Symptoms deserve care even when the pattern is unclear.

If tracking is burdensome, bring a brief summary rather than a perfect chart. Recording experiences should help an appointment, not make someone wait through severe pain or urgent bleeding before seeking help.

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Chapter 20

PMS, PMDD and cyclical symptoms

Recognising the pattern

Premenstrual symptoms can include breast tenderness, bloating, fatigue, sleep changes and mood changes. Premenstrual syndrome, or PMS, describes symptoms that recur before a period and improve afterwards, with enough effect on life to warrant attention. Symptoms are real even when routine hormone levels are not abnormal.

Premenstrual dysphoric disorder, or PMDD, is a severe premenstrual condition with marked psychological symptoms and impairment. Assessment considers timing and severity and other explanations, including depression or anxiety that may also worsen before a period. An existing mental health condition and a premenstrual pattern can coexist.

RCOG recommends keeping a symptom diary for at least two consecutive cycles. Record symptom-free days as well as difficult days. A diary can support diagnosis and show whether treatment helps, but someone at immediate risk of self-harm should seek urgent help rather than waiting to complete one.

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Treatment choices and review

RCOG describes approaches including information, exercise, cognitive behavioural therapy, certain combined hormonal contraceptives and antidepressants such as SSRIs. Choice depends on the most disruptive symptoms, contraception needs, health history and preferences. Some medicines may be taken continuously or during the premenstrual phase, guided by a prescriber.

For severe symptoms that have not responded to initial care, specialist assessment may include treatments that suppress ovarian activity. These have important effects and monitoring needs. Discuss expected benefit, adverse effects, duration and what happens if treatment is stopped.

Choose an outcome that matters, such as fewer days unable to work or reduced disruption to relationships. Review after an agreed interval. A normal blood test does not invalidate a severe cyclical symptom.

Sources for this section

Royal College of Obstetricians and Gynaecologists: Managing premenstrual syndrome (https://www.rcog.org.uk/for-the-public/browse-our-patient-information/managing-premenstrual-syndrome-pms/)

Distress and immediate support

Severe premenstrual mood symptoms can include hopelessness or suicidal thoughts. Tell a GP or mental health professional about their timing and intensity, including symptoms present outside the premenstrual window. Ask for a safety plan as well as treatment for the cyclical pattern.

If a person is in immediate danger, has acted on suicidal thoughts or cannot stay safe, call 999 or go to A&E. NHS 111 and an urgent GP appointment can help when a situation needs urgent assessment but is not immediately life-threatening.

People may be reluctant to disclose distress because they fear dismissal or stigma. A trusted person can accompany them if they wish. A safe assessment listens to the experience and considers wider health, not just the cycle date.

Sources for this section

Royal College of Obstetricians and Gynaecologists: Managing premenstrual syndrome (https://www.rcog.org.uk/for-the-public/browse-our-patient-information/managing-premenstrual-syndrome-pms/)

Chapter 21

PCOS: recognising the whole condition

Symptoms, biology and diagnosis

Polycystic ovary syndrome, or PCOS, is a varied condition involving reproductive, metabolic and psychological features. Irregular ovulation can produce widely spaced periods. Androgen-related features can include unwanted terminal hair growth, acne or scalp hair thinning. Not everyone has every feature, and PCOS can occur at different body sizes.

The 2023 international guideline uses a combination of irregular ovulation, clinical or biochemical androgen excess, and polycystic ovarian morphology or, in appropriate adults, anti-Müllerian hormone (AMH), after other causes are considered. AMH is not a stand-alone diagnosis. If irregular cycles and androgen excess are both present, ovarian imaging or AMH is not required under that framework.

In adolescents the guideline requires both ovulatory dysfunction, defined according to years after the first period, and clinical or biochemical hyperandrogenism. Ultrasound and AMH are not recommended for diagnosis in adolescents because normal maturation complicates interpretation. This is an international guideline, so a UK clinician also considers current local practice.

Sources for this section

Other explanations and rapidly changing symptoms

An irregular or absent period is not automatically PCOS. Pregnancy, thyroid disease, high prolactin, hypothalamic suppression associated with low energy availability, premature ovarian insufficiency and other conditions may be relevant. Assessment depends on age, symptoms, medicines, medical history and examination.

Rapid progression of marked facial or body hair growth, new voice deepening, increased muscle bulk or other signs of virilisation needs prompt specialist assessment. These features can indicate a different androgen-excess cause that should not be assumed to be ordinary PCOS. The speed of change matters as well as the hormone concentration.

Tell the clinician about hormonal contraception and any androgen products or supplements. The combined pill changes sex hormone binding and can make biochemical androgen assessment difficult. Do not stop contraception without discussing safe alternatives and the purpose and timing of testing.

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Insulin, glucose and endometrial health

Insulin resistance can be involved in PCOS, but it is not visible from body size and a single commercial insulin score is not a complete diagnosis. The international guideline states that routine insulin assays have limited clinical relevance and are not recommended in routine care.

PCOS is associated with increased risk of impaired glucose regulation and type 2 diabetes. The guideline considers a 75-gram oral glucose tolerance test the most accurate way to assess glycaemic status in PCOS; if it cannot be done, fasting glucose or HbA1c can be considered with reduced accuracy. Testing and follow-up should be adapted to individual circumstances and UK practice.

Long-standing infrequent or absent periods can leave the endometrium exposed to prolonged unopposed oestrogen and are associated with increased endometrial hyperplasia and cancer risk. The absolute risk remains low. Discuss cycle regulation or endometrial protection and assessment of unusual bleeding with a clinician rather than waiting for a fertility goal.

Sources for this section

International evidence-based guideline for assessment and management of PCOS, 2023 (https://pmc.ncbi.nlm.nih.gov/articles/PMC10505534/)

Chapter 22

PCOS care and reproductive goals

Matching care to individual priorities

A person may want help with cycles, hair growth, acne, emotional health, metabolic risk, fertility, or several concerns at once. The international guideline emphasises shared decisions and attention to weight stigma, anxiety, depression and quality of life. A single weight target should not displace care for the symptoms the person came to discuss.

The combined oral contraceptive pill can be considered for irregular cycles and hyperandrogenism when suitable. Other options, including metformin for selected metabolic indications or other treatments for hair growth, involve different benefits and risks. A clinician can explain contraception requirements where a treatment could harm a pregnancy.

Discuss the expected time to see an effect, costs, side effects and a review date. Someone seeking pregnancy needs a different plan from someone who wants contraception, and someone with contraindications to combined contraception may need alternatives.

Sources for this section

International evidence-based guideline for assessment and management of PCOS, 2023 (https://pmc.ncbi.nlm.nih.gov/articles/PMC10505534/)

Food, activity and stigma

The international guideline recommends healthy lifestyle support for people with PCOS, including eating and activity patterns that can improve health and wellbeing even without weight loss. It finds no evidence that one particular dietary composition or exercise type is universally superior for PCOS.

Choose a sustainable pattern that provides enough food, respects culture and budget, and fits existing health conditions. Movement can be built around ability and enjoyment. Extreme restriction or exercise intended to force hormones into a purchased target may create additional problems.

If weight management is requested, discuss respectful, evidence-based options and screen for eating concerns where appropriate. Being told only to lose weight is not a full investigation of irregular bleeding, distress or fertility concerns. Request a plan that addresses symptoms and risks directly.

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PCOS and conception

Irregular ovulation can make conception less predictable, but PCOS does not mean pregnancy is impossible. Evaluation considers ovulation and other relevant factors, including sperm and tubal factors when appropriate. Pregnancy can occur even after a long interval without a period, so contraception remains relevant if pregnancy is not desired.

For infertility due to anovulatory PCOS without other infertility factors, the international guideline recommends letrozole as first-line pharmacological ovulation induction where appropriate. This is an international recommendation; prescribing, licensing and local pathways should be discussed with a UK fertility specialist. Treatment requires clinical supervision.

The guideline also notes higher risks for some pregnancy complications in PCOS. A preconception discussion can consider glucose assessment, medication, folic acid and other individual needs. A risk association is not a prediction that a particular pregnancy will have a complication.

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Chapter 23

Absent periods and low energy availability

Amenorrhoea is a sign, not a diagnosis

Amenorrhoea means periods are absent. Pregnancy is an important early consideration when relevant, including after an apparently minor change in bleeding or while using contraception. Other possibilities include breastfeeding, hormonal medication, PCOS, thyroid or prolactin disorders, hypothalamic suppression, ovarian insufficiency and uterine or outflow problems.

The history includes the previous cycle pattern, likelihood of pregnancy, medications, weight and eating changes, activity, illness, stress, headaches, visual symptoms and nipple discharge. Assessment and tests are selected from the history rather than treating a missing period as proof of one hormone deficiency.

A person who has never started periods needs a different assessment from someone whose established periods stop. Ask a GP when to investigate your pattern. Severe abdominal pain, fainting or bleeding in a possible pregnancy needs urgent assessment, not a routine amenorrhoea work-up.

Sources for this section

Functional hypothalamic amenorrhoea

Functional hypothalamic amenorrhoea can occur when reproductive signalling is suppressed in the setting of stress, energy deficit, weight loss or intense exercise. The Endocrine Society guideline describes it as a diagnosis of exclusion: clinicians first consider pregnancy and other relevant endocrine or structural causes. It is possible at different body sizes.

Low energy availability means insufficient energy remains for physiological functions after accounting for activity. It may be intentional, unintentional or associated with disordered eating. Reduced hypothalamic signalling can affect gonadotrophins and ovarian function; prolonged sex hormone deficiency and inadequate nutrition can affect bone health.

Care can involve restoring energy balance through increased intake, improved nutrition or reduced exercise, alongside psychological support and management of an eating disorder if present. A multidisciplinary team can make changes safely. The US Endocrine Society guideline is not a UK service-eligibility policy.

Sources for this section

Endocrine Society: Functional hypothalamic amenorrhoea clinical practice guideline (https://www.endocrine.org/clinical-practice-guidelines/hypothalamic-amenorrhea)

Bone health and follow-up

The Endocrine Society guideline recommends a bone mineral density assessment after six or more months of amenorrhoea, or earlier when severe nutritional deficiency, energy deficit or skeletal fragility is suspected. The timing and availability of assessment should be discussed with the clinical team.

A withdrawal bleed induced by hormones does not by itself prove normal ovulation or that energy balance has recovered. The guideline advises against prescribing combined oral contraceptives solely to regain menses or improve bone density in functional hypothalamic amenorrhoea. Treatment requires attention to the underlying cause and contraceptive needs.

A review plan can include eating and activity support, symptoms, reproductive goals and bone risk. If periods remain absent, revisit the diagnosis and barriers to treatment rather than blaming the person. Do not begin or stop hormone medication without discussing the reason and alternatives.

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Chapter 24

Endometriosis, pelvic pain and bleeding

What endometriosis can involve

Endometriosis involves tissue similar to the lining of the womb growing outside it. It can cause inflammation and pain, and may be associated with adhesions or ovarian endometriomas. Symptoms may include period pain affecting daily life, persistent pelvic pain, pain during or after sex, cyclical bowel or bladder symptoms, and difficulty conceiving. The extent seen on imaging does not reliably measure pain severity.

NICE advises considering endometriosis in people with relevant symptoms, including adolescents. It also recognises that it can coexist with other conditions. Symptoms should be taken seriously even if they are difficult to describe or vary over the cycle.

A diary can record pain, bleeding, bowel or urinary symptoms, timing and effects on daily activities. A GP may discuss examination, ultrasound, treatment and referral depending on circumstances and the person's consent.

Sources for this section

NICE NG73: Endometriosis, diagnosis and management (https://www.nice.org.uk/guidance/ng73/chapter/recommendations)

Normal imaging does not exclude it

NICE recommends transvaginal ultrasound for suspected endometriosis, including when examination is normal, to identify ovarian endometriomas or deep disease and to look for other pathology. If a transvaginal scan is declined or unsuitable, transabdominal ultrasound can be considered. Consent and an explanation of the procedure matter.

Do not exclude endometriosis because an ultrasound or examination is normal. NICE recommends considering referral and, when appropriate, laparoscopy even after normal imaging. CA125 should not be used to diagnose endometriosis. The choice of investigations depends on symptoms, goals and specialist assessment.

A scan can answer some important questions while missing superficial disease. If symptoms continue, ask what the result rules in or out, what the next step is and when to review. Pain relief does not need to wait until every test is complete.

Sources for this section

NICE NG73: Endometriosis, diagnosis and management (https://www.nice.org.uk/guidance/ng73/chapter/recommendations)

Treatment, fertility and shared decisions

NICE describes pain management, hormonal treatment such as the combined pill or a progestogen, and specialist referral or surgery where appropriate. Hormonal treatment may reduce pain, but choice depends on pregnancy plans and individual circumstances. It is not a diagnostic test for the disease.

Persistent or recurrent symptoms, suspected deep endometriosis or an endometrioma may require specialist care. Surgery has potential benefits and harms, including effects on ovarian reserve in relevant procedures. Discuss the aim, alternatives, possible recurrence and fertility implications before deciding.

Heavy or irregular bleeding can have causes other than endometriosis. A clinician can consider other uterine, hormonal, pregnancy-related or medication causes. Any bleeding after menopause needs assessment, even if earlier cycles were painful.

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Chapter 25

Fertility: finding the right questions

More than an ovarian hormone result

Conception requires several processes to coincide: an egg must be released, sperm must reach it, and the reproductive tract and uterus must allow fertilisation and implantation. Age, ovulation, sperm, tubes, uterine conditions, health and medicines may all be relevant. Investigations are guided by circumstances, rather than a single universal panel.

NICE recommends asking about menstrual frequency and regularity. Regular monthly cycles make ovulation likely, although fertility investigation may include a properly timed progesterone test. Tubal assessment is selected according to medical history; a hormone test cannot establish whether tubes are open.

For semen analysis, collection instructions and the laboratory method matter. NICE recommends repeating an abnormal first result, ideally after three months, while severe sperm deficiency warrants earlier repeat testing. A reference value is not a sharp dividing line between fertile and infertile.

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AMH and ovarian response

Anti-Müllerian hormone is produced by cells in developing ovarian follicles. NICE advises using AMH or antral follicle count to help predict ovarian response and inform assisted-conception decisions and counselling. Results are interpreted alongside age and the full clinical situation.

NICE says not to use AMH as a predictor of clinical pregnancy through spontaneous conception. A low result does not mean spontaneous pregnancy is impossible; a high result does not guarantee it. An AMH test cannot measure egg quality in an individual or supply a reliable personal date for menopause.

NICE also advises against using FSH to predict ovarian response or the outcome of assisted conception. Before buying a fertility package, ask what each marker can predict, which decision would change and whether a consultation and follow-up are included.

Sources for this section

NICE NG257: Fertility problems, investigations and management (https://www.nice.org.uk/guidance/ng257/chapter/Investigation-of-fertility-problems-and-management-strategies)

Making a plan for investigation

When conception has not happened as expected, a GP or fertility service can discuss the history and appropriate timing of assessment. Seek advice earlier when there is a known condition or concern affecting fertility. Tests and eligibility for NHS-funded treatment depend on current guidance and commissioning arrangements; ask the service about your circumstances.

NICE recommends progesterone in the mid-luteal phase, adapting timing for longer or irregular cycles, and selected tests for anovulation or relevant symptoms. Prolactin is not a routine fertility test for everyone: NICE limits it to circumstances such as ovulatory disorder, galactorrhoea or pituitary tumour.

A useful appointment covers emotional support, treatments already tried, reproductive goals and what happens after each result. If more than one person is involved, offer assessment that considers each relevant contribution rather than placing all responsibility on the person who may carry a pregnancy.

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Chapter 26

Contraception and hormone interactions

How methods differ

Contraception includes non-hormonal options such as condoms and the copper intrauterine device, and hormonal options including combined or progestogen-only pills, implants, injections and hormonal intrauterine systems. Methods differ in how they prevent pregnancy, how often action is needed, bleeding effects, contraindications and reversibility.

Combined methods contain oestrogen and a progestogen and can suppress ovulation. Some progestogen-only methods suppress ovulation, while effects on cervical mucus and the uterine lining also matter. A scheduled bleed on some hormonal methods is not necessarily a natural menstrual period or proof of ovulation.

A contraceptive consultation should include preferences, medications, medical history and protection against sexually transmitted infections. Condoms help reduce STI transmission; many other contraceptive methods do not. Ask what to do if a pill is missed or a device is expelled.

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Benefits, risks and personal fit

Combined hormonal contraception can help some people with painful or heavy periods and can be used in management of selected conditions. It also has risks, including blood clots, and is unsuitable for some people depending on history and risk factors. The NHS describes the absolute clot risk as small; an individual discussion is more useful than applying one number to everyone.

Unexpected bleeding, breast tenderness or other effects can occur. If a method is unpleasant or unsuitable, ask about alternatives rather than stopping without a plan if pregnancy prevention matters. Sudden chest pain, breathlessness or a painful swollen leg during combined contraception needs urgent medical assessment.

Hormonal contraception can change laboratory interpretation. Tell the clinician the formulation and when it was started. Stopping solely to obtain a clearer test result can create pregnancy risk, so decide together whether a test is necessary and how to provide alternative contraception if needed.

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Herbs, medicines and effectiveness

St John's wort can reduce the effectiveness of hormonal contraceptives, including implants, by inducing medicine-metabolising enzymes. The MHRA has reported unplanned pregnancies and bleeding with the combination. Check with a pharmacist before using herbal products, and mention all medicines and supplements at a contraception review.

MHRA advice states that people using oral contraception and tirzepatide should add a barrier method or switch to a non-oral contraceptive for four weeks after starting tirzepatide and for four weeks after each dose increase. The advice is specific to tirzepatide, not a rule to apply automatically to every GLP-1 medicine.

Vomiting or severe diarrhoea can affect absorption of oral contraception. Follow the instructions for the specific method and ask a pharmacist or sexual health service about additional protection and emergency contraception when relevant. Check current medicine guidance before making changes.

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Chapter 27

Pregnancy and preparation

Hormones during pregnancy

After implantation, human chorionic gonadotrophin (hCG) supports the corpus luteum in early pregnancy. Pregnancy tests detect hCG. The placenta then becomes an important source of hormones, including progesterone and oestrogens, as pregnancy progresses. Hormones and circulating binding proteins change substantially during pregnancy.

A pregnancy test answers a specific question; timing can affect its result. If symptoms or clinical circumstances suggest an ectopic pregnancy, a negative early test or a presumed normal hormone level should not replace urgent assessment. Clinicians may use serial blood tests and ultrasound in the right setting.

Pregnancy can change the interpretation and treatment of pre-existing endocrine conditions. Arrange an early review of prescribed medicines and monitoring with the relevant team. Do not abruptly stop essential medication without advice.

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Folic acid and nutritional care

NICE recommends 400 micrograms of folic acid daily for anyone who may become or is planning to become pregnant, and during the first 12 weeks of pregnancy. Ideally start three months before trying, or as early as possible after a positive test. The recommendation applies even when foods are fortified.

NICE recommends a prescribed 5 mg daily for selected higher-risk circumstances, including a previous neural tube defect, certain family histories, type 1 or type 2 diabetes, and medicines that affect folate absorption or metabolism. In its 2025 recommendation, BMI of 25 or more alone is not a reason for the higher dose. Ask for individual advice, especially after bariatric surgery.

NICE also recommends discussing vitamin D and other nutrition during pregnancy and breastfeeding, including available Healthy Start support. A balanced, affordable diet and appropriately selected supplementation are more useful than a broad hormone supplement package. Check products and medications with a midwife, pharmacist or clinician.

Sources for this section

NICE NG247: Maternal and child nutrition (https://www.nice.org.uk/guidance/ng247/chapter/Recommendations)

Antenatal care and symptoms

Contact maternity services early when pregnant and discuss previous complications, chronic conditions and medicines. Antenatal care includes planned checks, information and decisions about screening. Needs differ, and appointments are opportunities to ask what a proposed test or intervention means.

Nausea, tiredness and bodily changes may occur in pregnancy, but severe symptoms should not be automatically dismissed as normal hormones. Dehydration, severe pain, bleeding, severe headache or other concerning change warrants prompt advice from the maternity team, NHS 111 or emergency services according to severity.

An ectopic pregnancy is a pregnancy outside the womb and can become life-threatening. One-sided lower abdominal pain, bleeding or shoulder-tip pain with a possible pregnancy warrants urgent advice. Sudden intense pain, fainting or collapse requires 999 or A&E.

Sources for this section

Chapter 28

After birth: hormones, feeding and recovery

Placenta, milk production and changing cycles

After birth, delivery of the placenta brings a marked change in circulating pregnancy hormones. Prolactin helps support milk production and oxytocin helps milk release during feeding. Feeding experiences and milk supply vary, and practical support matters. Hormone biology should never be used to blame a parent for feeding difficulties.

Breastfeeding can suppress ovulation, but its contraceptive reliability depends on specific conditions and timing. A period need not return before the first ovulation. The NHS says pregnancy is possible from three weeks after birth, even if breastfeeding and periods have not returned.

Discuss an appropriate contraceptive method with the midwife, GP or sexual health service. Different methods can be started at different times and have different considerations during feeding. If pregnancy is desired later, ask how pre-existing conditions and medicines should be reviewed.

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Postpartum thyroiditis and persistent symptoms

Postpartum thyroiditis is inflammation of the thyroid occurring after pregnancy. It can include a temporary overactive phase followed by an underactive phase, though not everyone experiences both. Palpitations, fatigue, anxiety, low mood or difficulty coping may have several explanations, and thyroid blood tests can help when clinically indicated.

Some people recover normal thyroid function; others develop longer-term hypothyroidism and need follow-up. The British Thyroid Foundation notes that thyroiditis can recur after another pregnancy. Treatment depends on the phase, symptoms and results, so self-starting iodine or thyroid products is not a substitute for assessment.

NICE recommends a GP postnatal assessment at six to eight weeks and opportunities to discuss physical and mental health. Persistent exhaustion deserves a broad assessment, which might consider sleep, blood loss, mood, infection and thyroid disease according to the history.

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Mental health and urgent postnatal signs

Mood changes after birth can have many forms. Postpartum psychosis is a psychiatric emergency and may involve hallucinations, unusual beliefs, severe confusion or a rapidly changing mood. If suspected, seek immediate assessment through maternity or mental health services; if there is immediate danger, call 999 or go to A&E.

NICE advises seeking medical advice without delay for sudden or very heavy bleeding, fever and pelvic pain, chest pain, shortness of breath, leg swelling and tenderness, or persistent severe headache after birth. Severe breathlessness, chest pain, collapse or overwhelming bleeding may require 999.

At any postnatal contact, discuss concerns about bleeding, pain, feeding, mood and practical support. Having a baby is a major physical transition, but a serious symptom should not be attributed to normal hormonal change without assessment.

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Chapter 29

Perimenopause and menopause

Changes in cycles and symptoms

Perimenopause is the transition towards menopause, during which ovarian activity and cycle patterns change. Periods may become irregular, with intervals and flow changing. Hot flushes, night sweats, sleep disturbance, changes in mood, joint discomfort or vaginal dryness may occur, but experiences differ greatly.

Menopause is identified retrospectively after 12 months without a period when hormonal contraception is not obscuring the pattern. Menopause can occur earlier following treatment or surgery. Symptoms can begin before periods end and may continue afterwards.

The same symptoms can have other explanations. New, severe or unusual symptoms deserve assessment rather than automatic attribution to menopause. Describe the impact on sleep, work, relationships and daily life so a plan can address the experiences that matter most.

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When a blood test helps and when it does not

NICE recommends identifying perimenopause or menopause without laboratory tests in otherwise healthy people aged 45 or over with the relevant symptoms and menstrual pattern. Hormones can fluctuate during the transition, so one result may not resolve the question. NICE does not recommend AMH, oestradiol or ultrasound measures to identify menopause in this age group.

NICE says to consider serum FSH to confirm menopause in people aged 40 to 45 with symptoms and a cycle change, or under 40 when menopause is suspected. It advises against using FSH to identify menopause while someone uses combined oestrogen-progestogen contraception or high-dose progestogen.

Hormonal treatments and hysterectomy can make the bleeding history harder to interpret. A clinician can consider the whole pattern, treatment and age. NICE NG23 does not cover people currently taking gender-affirming hormone therapy; it makes specific recommendations for some people who have used it in the past.

Sources for this section

NICE NG23: Menopause, identification and management (https://www.nice.org.uk/guidance/ng23/chapter/recommendations)

Managing symptoms and protecting wellbeing

NICE recommends offering HRT for menopause-associated vasomotor symptoms, and considering menopause-specific CBT alongside HRT, when HRT is contraindicated, or when preferred. NICE also recommends fezolinetant as an option for moderate to severe vasomotor symptoms when HRT is unsuitable, in line with its technology appraisal. Ask about monitoring, risks and availability.

For genitourinary symptoms such as vaginal dryness or discomfort, NICE recommends vaginal oestrogen for people without a history of breast cancer, with discussion of alternatives such as moisturisers and lubricants. Care differs for people with a breast cancer history and may involve a specialist. Vaginal symptoms deserve specific treatment rather than being overlooked.

Discuss bone health, activity that maintains strength, sleep and mental health. NICE does not recommend HRT solely to prevent dementia or cardiovascular disease. A plan can be adjusted as symptoms, preferences and medical circumstances change.

Sources for this section

NICE NG23: Menopause, identification and management (https://www.nice.org.uk/guidance/ng23/chapter/recommendations)

Chapter 30

Premature ovarian insufficiency and early menopause

A different life-stage and a different decision

Premature ovarian insufficiency, or POI, refers to loss of normal ovarian function before age 40. It may follow medical or surgical treatment, be related to an inherited or other condition, or have no identified cause. Early menopause occurs between ages 40 and 44. The diagnosis may affect symptoms, fertility, bone health and emotional wellbeing.

NICE uses the clinical picture, including absent or infrequent periods, together with elevated FSH on two blood samples taken four to six weeks apart for diagnosis of POI in people under 40. It advises against diagnosis from a single blood test and against routine AMH testing for diagnosis. Hormone use and other explanations need consideration.

A diagnosis can bring grief, relief, uncertainty or several feelings at once. Ask about specialist support, fertility implications and whether further investigation of the cause is appropriate. The result does not define identity or decide whether a person wants children.

Sources for this section

NICE NG23: Menopause, identification and management (https://www.nice.org.uk/guidance/ng23/chapter/recommendations)

Hormone replacement and long-term health

NICE recommends offering people with POI a choice of sex steroid replacement with HRT or a combined hormonal contraceptive, unless contraindicated, and generally continuing treatment until at least the age of natural menopause. It explains the importance of treatment for bone and cardiovascular health and discussing individual benefits and risks.

HRT and combined contraception are not interchangeable for every purpose. HRT is not a contraceptive. Some ovarian activity and spontaneous conception can occur with POI, so discuss reliable contraception if pregnancy is not desired and specialist fertility advice if it is.

The evidence used for symptom treatment after typical-age menopause should not simply be applied to younger people with POI without considering age and circumstances. NICE recommends review, information and psychological support; treatment can be reconsidered as circumstances change.

Sources for this section

NICE NG23: Menopause, identification and management (https://www.nice.org.uk/guidance/ng23/chapter/recommendations)

Treatment-induced menopause and fertility conversations

Cancer treatment, surgery or other medical care may affect ovarian function. Whenever possible, discuss potential menopause and fertility effects with appropriate specialists before treatment and again afterwards. The urgency of treating the underlying condition and the person's priorities both matter.

Fertility preservation may involve specialised choices with different requirements and uncertainties. Ask what is feasible in the time available, how treatment may affect the options and what follow-up is planned. A service can explain the current local pathway without promising an outcome.

After treatment, new symptoms and bone or sexual health concerns deserve continued attention. If hormone therapy is unsuitable because of the underlying condition, ask for a discussion of alternatives and referral to a clinician with relevant expertise.

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Chapter 31

HRT: formulations, evidence and follow-up

Oestrogen, progestogen and route

Systemic menopausal HRT can be given in different preparations and routes, including tablets, patches and gels. NICE recommends combined HRT for people with a uterus and oestrogen-only HRT for those who have had a total hysterectomy. Progestogen is included with systemic oestrogen when needed to protect the uterine lining; the schedule and dose require clinical guidance.

Sequential and continuous combined regimens have different bleeding patterns and may suit different circumstances. Route matters: NICE reports higher venous thromboembolism risk with oral than transdermal HRT and recommends considering transdermal treatment for people at increased risk. This does not make any route risk-free or suitable for everyone.

A regimen is selected using age, symptoms, personal and family history, other medicines and preferences. Ask which preparation is prescribed, how to take it, what bleeding to expect, and what to do about missed doses or side effects.

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What trials can and cannot tell us

NICE presents benefits and risks separately for combined and oestrogen-only HRT, and considers age, route and duration. It reports increased breast cancer risk with combined HRT that rises with duration, and little or no increase with oestrogen-only HRT. Individual baseline risk and the indication for each regimen matter.

The Women's Health Initiative randomised trials and long-term follow-up studied specific oral preparations in postmenopausal participants with particular age and health characteristics. Their findings are important, but should not be assumed to measure every preparation, route, dose or younger population. Trial outcomes and duration must be read alongside current guidance.

HRT reduces fragility fracture risk while taken, and benefits and risks change with time. NICE provides decision aids for discussing absolute risks. Ask for a comparison relevant to your age and history rather than accepting either a blanket reassurance or a blanket warning.

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Bleeding and review

Bleeding patterns depend on the regimen and time since starting or changing treatment. NICE updated its guidance in 2026 on assessing unscheduled bleeding with systemic HRT. Report unexpected bleeding to the prescriber so they can assess timing, risk factors, examination and whether investigation is needed.

Any postmenopausal bleeding, even spotting or a single episode, should be checked by a GP. Do not assume it is harmless because HRT is being used. Heavy bleeding, feeling faint or severe symptoms need more urgent advice; if collapsed or severely unwell, call 999.

NICE recommends review of treatment after starting and regularly thereafter, discussing symptom response, side effects and the balance of benefits and risks. Agree who will arrange prescriptions and follow-up, and seek earlier review when a new concern arises.

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Chapter 32

Testosterone, sexual health and fertility

Symptoms and biochemical confirmation

Testosterone contributes to sexual function, body composition, bone and other processes. Low sexual desire, erectile difficulties and fatigue can arise from multiple causes, including medicines, sleep problems, diabetes, depression or relationship circumstances. These symptoms alone do not confirm testosterone deficiency.

UK laboratory guidance recommends interpreting testosterone with symptoms and obtaining a morning, fasting sample in the appropriate setting, with repeat testing when low or borderline. Acute illness and food intake can affect values. Sex hormone-binding globulin (SHBG) and calculated free testosterone can help in selected situations where binding differs.

LH and FSH can help distinguish testicular from hypothalamic or pituitary patterns after a low result is confirmed. Further investigation depends on the history and results. Lab method, reference interval and the units on the report matter; do not compare results blindly with a marketed target.

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Treatment, monitoring and conception

Testosterone treatment is considered for confirmed hypogonadism in an appropriate clinical context, not automatically for ageing or nonspecific fatigue. Treatment choices require discussion of expected effects, contraindications and monitoring, including blood count and other checks selected for the individual.

External testosterone can suppress gonadotrophin signalling and sperm production. The Endocrine Society advises against starting testosterone therapy in people planning fertility in the near term. Discuss reproductive goals and possible alternatives with an endocrinologist or fertility specialist before treatment; recovery after stopping is not guaranteed or immediate.

TRAVERSE studied a specified testosterone gel regimen in men with hypogonadism and pre-existing or high cardiovascular risk. It found noninferiority for its primary major cardiovascular event outcome over the study period, while some adverse events were more frequent. This does not establish safety for every dose, product, patient or long-term use.

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Low desire in menopause and broader sexual wellbeing

Sexual wellbeing involves desire, comfort, relationships, body image, medicines, physical health and personal goals. Vaginal dryness or pain can be treated directly. Low desire should not be reduced to a single testosterone value, and people differ in whether they want treatment.

NICE advises considering testosterone for low sexual desire associated with menopause if HRT alone is not effective; it notes that this use was off-label at the time of the recommendation. The international consensus identifies evidence for postmenopausal women with hypoactive sexual desire disorder following a full assessment, not for general energy or anti-ageing treatment.

Prescribing and monitoring should avoid testosterone concentrations substantially above the intended physiological range and consider adverse effects. Ask about the evidence for your situation, formulation, expected trial duration, follow-up and what will happen if symptoms do not improve.

Sources for this section

Chapter 33

Gender diversity, anatomy and hormone care

Care starts with the person

Gender identity, sex characteristics, anatomy and hormone treatment history are related to health in different ways. Trans, non-binary and intersex people have varied bodies and experiences. A respectful consultation asks which terms the person prefers, what organs are present and what care they need, rather than inferring anatomy or pregnancy potential from identity.

A person with a cervix, uterus, ovaries, testes or prostate may need care relevant to those organs, depending on individual history. Screening invitations may not always reflect a person's anatomy or registration details, so ask a GP or screening service how to access the appropriate programme. Consent and privacy matter.

Differences in sex development encompass diverse variations in chromosomes, hormones or reproductive anatomy. The NHS describes different causes and individual care needs. An intersex trait does not establish a person's gender identity, fertility or treatment preference.

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Hormone therapy, monitoring and fertility

Gender-affirming hormone treatment can change hormone concentrations, physical characteristics and the interpretation of laboratory results. The 2017 Endocrine Society guideline discusses monitoring and fertility counselling. It is an international clinical guideline, not a statement of current UK eligibility or prescribing policy.

Discuss fertility goals and preservation options before treatment when possible, including uncertainties, costs and timing. Testosterone is not a reliable contraceptive, and suppressed bleeding does not prove pregnancy is impossible. Decisions about pregnancy prevention depend on anatomy, sexual activity and personal goals.

If a laboratory result is unexpected, the clinician and laboratory should consider the actual treatment, organs, clinical question and assay rather than relying on a reference interval attached automatically to a registration marker. Do not alter or interrupt treatment without discussing the decision with the prescribing team.

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Menopause and individual context

A person with ovaries can experience changes in ovarian function even when menstrual bleeding is suppressed or absent. Surgery, medicines and current or past hormone treatment change how symptoms and tests are interpreted. Pain, bleeding or vasomotor symptoms deserve assessment without assumptions about identity.

NICE NG23 does not cover people currently having gender-affirming hormone therapy. For trans men and non-binary people registered female at birth who have used it in the past and now have menopause symptoms, it recommends access to a clinician with menopause expertise and describes menopause-specific CBT as an option.

Ask the team which evidence applies to your situation and where specialist advice is needed. If a service cannot answer, request an appropriate referral and a plan for symptoms while that advice is sought. Access to respectful care matters as much as the laboratory result.

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Chapter 34

Hormone blood tests: from question to result

A test needs a clinical purpose

A useful hormone test starts with a question: for example, whether ovulation occurred, whether symptoms fit a thyroid or pituitary problem, or whether a person with compatible symptoms has biochemical testosterone deficiency. The question determines which sample, timing and follow-up are appropriate.

A reference interval describes results in a defined reference population using a particular method. It is not a promise of perfect health, and a value just outside it does not automatically establish disease. A result within the interval can still be important when the history, timing or paired hormone suggests a problem.

Ask who will review the result, when you will hear back, what an abnormal result might mean and whether repeat testing or referral is planned. A report without a clinical plan may produce uncertainty without answering the original concern.

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Timing, medicines and binding proteins

Some hormones follow daily rhythms, and others vary across the menstrual cycle. A testosterone sample may be requested in the morning and fasting; progesterone for ovulation is timed to the luteal phase; cortisol testing has its own timing. Record sleep pattern and cycle day when relevant, and follow the laboratory's instructions.

Medicines can affect production, binding proteins or measurement. Oral oestrogen changes cortisol binding and can raise measured total serum cortisol. NICE has specific advice for preparation before cortisol testing; discuss changes with the ordering clinician because stopping contraception or HRT without a plan can have consequences.

Hormonal contraception, testosterone, glucocorticoids, pregnancy and acute illness can all change interpretation. Bring a list of prescribed and non-prescribed medicines and supplements, including doses and recent injections. Never stop prescribed glucocorticoids abruptly to prepare for a test.

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Repeat results and clinical context

A repeat sample can distinguish a persistent abnormality from temporary change, measurement variation or a result taken at an unsuitable time. Some conditions have specific repeat-testing recommendations, while others require rapid action. The correct interval depends on the clinical question.

Ask whether the same laboratory and assay should be used for comparison. Different methods and units can produce numbers that are not directly interchangeable. A trend can help, but it is not meaningful without consistent conditions and an explanation of what change would alter care.

Normal initial tests do not mean a person's symptoms are imagined. Equally, an unexpected minor abnormality does not necessarily explain every symptom. Discuss follow-up and alternative explanations, especially when the condition or symptom pattern changes.

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Chapter 35

Assays, interference and reference ranges

What laboratories actually measure

Immunoassays use antibodies to detect a target; mass spectrometry uses a different analytical approach and can be useful for selected hormones and concentrations. The best method depends on the substance, clinical purpose, laboratory quality and available validation. No method eliminates every possible source of error.

Hormones may circulate bound to proteins as well as in an unbound fraction. Total testosterone includes bound hormone, while calculated free testosterone uses total testosterone, SHBG and assumptions in a calculation. Direct measurements and calculated estimates have different limitations; the result should match the clinical question.

A measurement tells us the concentration in the sample under the conditions of the assay. It does not directly display hormone action in every tissue or prove that a symptom is caused by that concentration.

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Biotin and other misleading results

Some supplements contain biotin, including products marketed for hair and nails. Biotin can interfere with certain immunoassays, producing falsely high or low results depending on the assay design. Other interferences include antibodies and related substances in the sample. The pattern can look biologically plausible or highly contradictory.

If a result does not fit symptoms or other results, a clinician can ask the laboratory about interference, repeat the sample under suitable conditions or use another validated method. Do not independently discontinue needed medication. Ask how long a biotin-containing supplement should be withheld for the specific assay and dose.

An interference investigation is especially important when a result could lead to major treatment, imaging or surgery. Inform the team about supplements before the blood draw rather than waiting until after an unexpected result.

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Reference interval versus marketed optimal range

A laboratory reference interval is derived from a defined population and method, often with age, sex or physiological context considered. It is not the same thing as a treatment threshold established in studies of a particular condition. Some legitimate thresholds depend on the test method, timing and clinical question.

A wellness report may mark values as suboptimal using a narrower proprietary band. Ask how that band was established, whether its use improves patient outcomes, and whether the proposed treatment has been compared with usual care. A coloured flag is not evidence that a person needs a hormone product.

There are no universal optimal hormone ranges that apply to all ages, cycle stages, bodies, treatments and assays. An individual result can be significant even within a population interval, but the explanation and next step must be grounded in the relevant clinical context.

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Chapter 36

Cortisol and dynamic endocrine tests

Adrenal insufficiency and morning cortisol

Cortisol follows a daily rhythm and supports blood pressure, glucose regulation and the response to physiological stress. Adrenal insufficiency is a recognised condition in which cortisol production is inadequate. Symptoms can include persistent fatigue, weight loss, nausea, dizziness and other signs; these are not specific to the condition.

NICE recommends an 8 to 9 am serum cortisol in people aged one year or over when adrenal insufficiency is suspected, with interpretation and next steps according to the guideline and assay. NICE's stated cut-offs apply to modern immunoassays; local advice is needed for alternative assays and special circumstances.

Glucocorticoid use, recent injections, oral oestrogen and age affect testing or interpretation. NICE advises against testing people taking oral glucocorticoids at physiological replacement doses or above in the initial pathway. Discuss preparation with the clinical team, and never stop steroids abruptly. Suspected adrenal crisis needs emergency treatment, not a delayed routine test.

Sources for this section

NICE NG243: Adrenal insufficiency, identification and management (https://www.nice.org.uk/guidance/ng243/chapter/Recommendations)

Why stimulation and suppression tests exist

A single concentration sometimes cannot show whether a gland can respond appropriately. A dynamic test changes an input and measures the response: a stimulation test asks whether hormone output rises when prompted, while a suppression test asks whether it falls when feedback is applied. Preparation, timing and interpretation are specific to each test.

For suspected adrenal insufficiency, a specialist may arrange an ACTH stimulation test when indicated. Other endocrine questions use different protocols. A test used to investigate one disorder should not be repurposed as a general stress score or interpreted with thresholds from another assay.

Ask why the test is recommended, what preparation is required, possible adverse effects and who will communicate the result. Acute illness or medicines may change the approach. A specialist interprets the result together with clinical history and other investigations.

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Adrenal fatigue is not the same diagnosis

Persistent exhaustion is real and deserves careful assessment. A systematic review found no substantiation for adrenal fatigue as a distinct medical condition, and the studies it reviewed used inconsistent methods and definitions. A commercial cortisol curve cannot establish that everyday stress has depleted the adrenal glands.

This conclusion does not mean fatigue is imagined, or that genuine adrenal insufficiency does not exist. NICE describes how to recognise and test for adrenal insufficiency. Other causes of fatigue, including sleep disorders, anaemia, medicines and many illnesses, may also need consideration.

Supplements marketed for adrenal support do not replace investigation or prescribed steroid replacement. If fatigue persists, ask what has been considered, which symptoms or changes need earlier review, and what practical support can be offered while the assessment continues.

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Chapter 37

Saliva, urine and commercial hormone panels

Different samples answer different questions

Hormones and their metabolites can be measured in blood, saliva or urine. Each sample has its own physiology, collection requirements, units and reference intervals. A value from one sample is not automatically equivalent to a value from another. The useful question is whether a particular test has been validated for the condition being investigated and will affect a decision.

Some saliva and urine tests have established roles in specific circumstances. The Endocrine Society's 2008 Cushing's syndrome guideline includes late-night salivary cortisol and 24-hour urinary free cortisol among initial tests for appropriately selected patients. Collection technique, timing, medication and the possibility of false results matter, and abnormal results need clinical interpretation. This international guideline is not a general recommendation to screen everyone with fatigue.

By contrast, NICE's initial pathway for suspected adrenal insufficiency uses an appropriately timed serum cortisol in eligible people, interpreted in context. A commercial daytime salivary curve should not be substituted for that pathway or used to diagnose a depleted adrenal gland. Ask the clinician and laboratory which sample and protocol fit the specific concern.

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What dried urine research can and cannot show

One small 2021 observational study compared dried and liquid urine measures and compared four dried spots with a 24-hour collection for selected reproductive hormones and metabolites. Agreement for the measurements studied was generally good to excellent. The researchers were employees of the company associated with the testing method, a relevant connection when judging independent replication.

That study tested analytical agreement: whether methods produced similar measurements in the people and circumstances studied. It did not establish that the panel diagnoses the cause of nonspecific symptoms, predicts individual disease or improves outcomes when used to choose supplements or HRT doses. A metabolite is not a direct measurement of a symptom's cause or of the hormone effect in every tissue.

Collection time, sample handling, metabolism and the laboratory method can influence results. Ask which individual markers are validated, in which populations and for which clinical decisions. A convenient collection method and many reported numbers do not by themselves establish clinical usefulness.

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Before buying a panel

Write down the decision the test is meant to inform. Ask what diagnosis is being considered, whether the test is recommended for that situation, how an abnormal and a normal result would each change care, and whether a more focused test or clinical assessment would answer the question. Broad panels can identify incidental deviations that lead to repeat tests and worry without explaining the original symptom.

Check who interprets the result, the laboratory method and relevant reference interval, total cost including follow-up, and the evidence behind any proprietary optimal range. Ask whether the practitioner also profits from supplements sold in response to the result. Commercial interests do not automatically make a service invalid, but they are relevant to informed choice.

At-home collection can reduce travel for some people. It still requires appropriate instructions and follow-up, particularly when an unexpected result might need timely care. Keep the report and units, and ask your GP or relevant specialist how it fits with symptoms, examination and any existing results rather than changing prescribed medicine on your own.

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Chapter 38

Body-identical and compounded hormones

The same phrase can describe different products

Some regulated, licensed HRT products contain hormones with the same molecular structure as hormones made by the body, such as estradiol and micronised progesterone. These are sometimes called body-identical. They are manufactured to regulated standards, have approved prescribing information and are selected according to the person's needs and circumstances.

Bespoke compounded products are prepared individually, sometimes combining multiple hormones in formulations outside the usual licensed products. The British Menopause Society distinguishes these from regulated body-identical preparations. An individualised prescription for a licensed product is not the same thing as an unlicensed compounded mixture.

Compounded products may be presented as more natural or inherently safer, but that description does not demonstrate superior clinical outcomes or consistent dosing. Discuss the ingredients, strength, route, regulation, evidence and monitoring with the prescriber. Licensed preparations can still have risks and side effects, and choosing between them requires an individual conversation.

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Why saliva-guided prescribing needs caution

Saliva hormone levels vary and do not reliably establish a personal hormone replacement dose. The British Menopause Society does not recommend saliva testing to determine a dose of compounded hormones. An attractive diagram showing a missing hormone or an ideal target is not evidence that the suggested dose is effective or safe.

HRT is generally reviewed by asking about symptoms, side effects, bleeding and individual risk, with the regimen adjusted by an appropriately qualified prescriber. A laboratory test can be appropriate for a specific question, but a panel is not a substitute for clinical review. NICE gives detailed recommendations for menopause care and unscheduled bleeding.

For someone with a uterus taking systemic oestrogen, an appropriate progestogen regimen is important to protect the endometrium. Different routes and doses require suitable prescribing. Seek advice for unexpected bleeding rather than assuming a personalised mixture is providing adequate protection.

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Making a treatment decision

Ask what symptom the treatment is intended to improve, the alternative options, expected benefits and risks for your age and history, and when you will review it. Clarify whether the product is licensed, how repeat prescriptions and safety checks work and what to do if the supply changes.

Evidence from a particular HRT trial cannot be assumed to apply equally to every dose, route, age or combination. The Women's Health Initiative follow-up describes participants and formulations studied; it does not settle the effects of every other preparation. NICE brings wider evidence into its current recommendations.

If you have started a private product, share the exact label, dose and ingredients with the NHS clinician involved in your care. Continue or change prescribed treatment only with appropriate advice, and do not ignore concerning symptoms while waiting for a routine review.

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Chapter 39

Food, energy and metabolic health

Enough nourishment before a restrictive protocol

Food supplies energy, protein, fats, carbohydrate, fibre and micronutrients used throughout the body. Hormone production and reproductive function depend on sufficient energy as well as many other signals. A balanced pattern over time is more useful than treating a single food as a hormone switch. NHS guidance describes a varied diet built around vegetables and fruit, higher-fibre carbohydrates, protein foods and appropriate sources of calcium and unsaturated fats.

Undereating relative to activity and other demands can contribute to functional hypothalamic amenorrhoea and affect bone health, even when a person does not fit a stereotyped picture of an eating disorder. Assessment includes pregnancy and other causes of absent periods. Increasing energy availability, reducing excessive training when relevant and appropriate psychological or dietetic support are part of care.

A restrictive detox diet can add cost and nutritional risk without proving that symptoms are caused by stored toxins. If you have food insecurity, allergies, disordered eating, pregnancy, a medical condition or difficulty eating, ask for practical help and individual dietary advice rather than following a generic restriction plan.

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Blood glucose and PCOS without a single perfect diet

Insulin helps regulate blood glucose and can also influence ovarian androgen production. Insulin resistance is common in PCOS, including in people across a range of body sizes. The international PCOS guideline recommends assessment of glycaemic status and identifies a 75 g oral glucose tolerance test as the most accurate approach in adults with PCOS, irrespective of BMI. Use and access should be discussed locally.

The same guideline finds no evidence that one diet composition is superior for all people with PCOS. A sustainable pattern can include regular meals, fibre-rich foods, protein and sources of unsaturated fat, adapted to preference, culture, cost and medical needs. Weight-neutral benefits of healthy behaviours matter too.

Do not assume a routine fasting insulin result provides a dependable personal insulin-resistance score: the international guideline does not recommend routine insulin assays in clinical care for PCOS. Ask which measures are needed for your individual risk and when they should be repeated.

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Life stage changes the nutritional question

Before and during pregnancy, nutritional priorities include folic acid and attention to safe food choices. NICE recommends 400 micrograms of folic acid daily before conception and through the first 12 weeks for most people, with specific higher-dose indications assessed individually. BMI alone is not a NICE indication for a higher dose. A clinician can review medicines and the correct dose before conception.

After menopause or with premature ovarian insufficiency, protecting bone health can become particularly important. Adequate calcium, vitamin D where indicated, appropriate activity and treatment of underlying causes are relevant parts of a wider plan. A supplement should address an identified need rather than a promise to reset hormones.

A registered dietitian can help translate a diagnosis into an eating pattern that is workable and nutritionally sufficient. For specialist or complex needs, ask whether referral is appropriate and whether an alternative, such as fortified foods or a prescribed supplement, is suitable.

Sources for this section

Chapter 40

Sleep, movement and stress in context

Sleep is a biological need, not a personal failure

Sleep and waking are coordinated by circadian signals and homeostatic sleep pressure. Hormonal changes, hot flushes, pain, anxiety, caring responsibilities, shift work and other conditions can disrupt sleep. Poor sleep may also intensify pain, affect concentration and make daily management harder, creating a cycle that deserves practical support.

A regular wake time where possible, a wind-down routine and a comfortable sleep environment can help. Caffeine, alcohol, noise and light can matter, but a person with a new baby, unstable housing, chronic pain or shift work may not be able to control all of these. Adapt advice to the life someone actually has.

Persistent snoring with breathing pauses, severe daytime sleepiness, repeated night waking or insomnia affecting daily life deserves assessment rather than an expensive hormone panel alone. For menopausal sleep disruption, discuss the flushes, pain or mood symptoms that may need treatment as well as sleep itself.

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Movement that fits the body in front of you

Movement can support cardiovascular fitness, strength, mood and metabolic health. UK adult guidance recommends being active regularly, including muscle-strengthening activity, with an overall weekly activity goal. The starting point can be smaller than the guideline, and age, disability, pregnancy, symptoms and medical conditions change what is appropriate.

For someone whose symptoms worsen substantially after exertion, a fixed progression plan may be unsuitable. Describe the timing and duration of symptom worsening to the clinician and ask for tailored advice. Pain, dizziness, unexpected bleeding or a new severe symptom during activity also deserves assessment.

Training more is not always better. When energy intake fails to meet the demands of movement and daily life, menstrual disruption and other consequences may follow. Rest, adequate food and a change in training load may form part of treatment for low energy availability. Avoid using exercise as a punishment for a laboratory value.

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Stress, support and the limits of cortisol stories

Stress responses involve the brain, nervous system and several hormones; they are designed to adapt to changing circumstances. Long-running pressures can affect sleep, mood, pain and health behaviours. Their effects are real, but a symptom after stress does not establish that stress is its only cause or that an adrenal gland has stopped working.

Useful support might include a trusted person, workplace adjustments, financial or housing advice, talking therapy, relaxation, time outdoors or treatment for an underlying mental health condition. Preferences and access differ. A symptom diary can sometimes reveal patterns, but constant monitoring can become burdensome, so agree what is useful and when to stop.

A clinician can investigate symptoms and support mental health at the same time. If a suggested strategy worsens distress, discuss another approach. Ask what further assessment is planned if symptoms persist rather than accepting a vague promise that a supplement will normalise a stress hormone.

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Chapter 41

Endocrine disruptors and environmental exposures

A plausible mechanism is not an individual diagnosis

Endocrine-disrupting chemicals can interfere with hormone signalling or other endocrine processes. Examples discussed by the US National Institute of Environmental Health Sciences include chemicals used in some plastics, pesticides, personal care products and industrial processes. People can encounter mixtures in food, water, air, consumer products and workplaces.

Whether a particular exposure causes harm depends on the substance, dose, timing, route, duration and the person exposed. Laboratory, animal and human studies answer different questions. An association in a population or an effect at a particular experimental dose does not establish that a specific symptom in an individual was caused by a particular household product.

Hormone symptoms have many possible explanations. A consumer hormone metabolite panel cannot identify the source or prove that an exposure is responsible. A clinician can assess relevant symptoms and, when there is a credible exposure history, consider occupational health or specialist advice.

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Practical choices without a fear-based detox

A proportionate approach can focus on known and avoidable routes: follow pesticide and household product instructions, use workplace protective measures when required, ventilate when appropriate and wash hands before eating after handling chemicals. Follow food-container manufacturer instructions, including for heating. These steps can be useful without implying that any single product has caused a hormone disorder.

Eating a varied diet and following UK food-safety advice is generally more practical than removing major food groups because of an unverified exposure claim. Different materials and products involve different trade-offs, and the safest choice should take affordability and accessibility into account.

The body has ordinary processes for transforming and eliminating substances through organs including the liver and kidneys. A commercial cleanse or hormone detox has not been shown to treat a generalised accumulation of endocrine disruptors. Some restrictive diets, high-dose supplements and unregulated products can themselves cause harm.

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When exposure needs specific help

For a workplace or acute exposure, record the product name, route, time, duration and symptoms if it is safe to do so. Follow the site's safety procedure and seek prompt medical or occupational health advice. Sudden severe symptoms or collapse require emergency help. Bring the packaging or safety information when available.

Pregnancy, infancy and other developmental stages can be sensitive periods for some exposures, but risk varies by chemical. Discuss a specific exposure with a midwife, GP or relevant service rather than assuming that all contact caused harm. Do not stop necessary prescribed treatment because a general online list labels it a chemical.

If an environmental concern persists, ask what is known about the actual exposure, whether a validated investigation exists, what alternative explanations remain and which practical action would make a difference. Public-health and workplace controls matter alongside individual choices.

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Chapter 42

Supplements and functional-health claims

What a supplement can and cannot establish

A supplement can be useful when it addresses a specific requirement or deficiency. Folic acid before and during early pregnancy is one example with clear guidance. The claim that a blend balances every hormone is different: it does not specify which condition is being treated, how the dose was tested or what improvement a person can expect.

Functional-health practitioners may take time to discuss sleep, food, stress and symptom patterns. These topics can be valuable when integrated with appropriate medical assessment. The label functional does not itself validate a diagnostic test, supplement combination or promise to reverse a disease. Ask what evidence supports the specific recommendation and how it will be reviewed.

Before buying, check the full ingredients and doses, possible medicine interactions, pregnancy and breastfeeding suitability, quality and total cost. Mention all products to your GP, pharmacist and laboratory, including hair and nail supplements containing biotin, which can interfere with some blood assays. Do not replace prescribed treatment with an unproven product.

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Inositol for PCOS and antioxidants for fertility

Inositol products are marketed for PCOS, often as myo-inositol or combinations with D-chiro-inositol. The 2023 international PCOS guideline says inositol can be considered according to individual preferences and values, noting limited harm and potential improvement in some metabolic measures, but limited clinical benefits including for ovulation, hirsutism or weight. It cannot currently recommend a particular type, dose or combination because evidence is insufficient.

For infertility associated with PCOS, the same international guideline considers inositol an experimental therapy with uncertain benefits and risks. Product quality and doses may vary. Discuss the specific reproductive goal, alternatives and whether an appropriately timed fertility assessment is needed, rather than assuming that a supplement will restore ovulation.

A Cochrane review of antioxidants for male subfertility found very low-certainty evidence for key outcomes. A supplement showing a change in a laboratory measure does not necessarily improve live birth. Investigate both partners where relevant, and discuss medicines, underlying causes and suitable treatment instead of delaying assessment while trying an expensive stack.

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DIM, tamoxifen and oestrogen metabolism

Diindolylmethane, or DIM, is sold with claims about changing oestrogen metabolism. Metabolites are products of biochemical processing, not simple labels for good and bad oestrogen. A different metabolite pattern does not establish that a person has lowered cancer risk or corrected a cause of symptoms.

In a randomised trial among women taking tamoxifen, DIM changed selected urinary oestrogen metabolite ratios but also reduced circulating concentrations of endoxifen, an important active tamoxifen metabolite. The clinical significance of this finding requires further study; it is not evidence that DIM improves cancer outcomes or is safe alongside tamoxifen.

If you take tamoxifen or another cancer medicine, check any supplement with your oncology team or pharmacist before use. Eating ordinary foods containing related compounds is a different exposure from taking a concentrated supplement. Never alter cancer treatment based on a commercial hormone metabolism report.

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Black cohosh, ashwagandha and herbal interactions

Black cohosh is marketed for menopausal symptoms, but studies use different preparations and evidence of benefit is uncertain. Liver injury has been reported in people taking black cohosh products, although a causal link has not been established in every case. If jaundice, dark urine or other signs of liver problems develop, stop the product and seek medical advice promptly.

Ashwagandha is marketed for stress and sleep. Some small studies suggest possible effects, but preparation and long-term safety questions remain. The US National Center for Complementary and Integrative Health notes rare liver injury reports, potential interactions with several medicines and cautions for people with thyroid or autoimmune disorders; it should be avoided during pregnancy and breastfeeding.

Herbs can interact with medicines even when sold without a prescription. For example, the MHRA warns that St John's wort can reduce the effectiveness of hormonal contraception, including implants. Ask a pharmacist about the exact product and prescribed medicines, and discuss evidence-based options for menopausal symptoms or persistent distress with a clinician.

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Chapter 43

Finding informed and inclusive care

Getting into the system

A GP appointment can be a starting point for a symptom history, examination if appropriate, focused tests and referral. In England, NHS guidance explains how to register at a GP surgery, including online or by paper form. The four UK nations have different administrative arrangements, so check the relevant local NHS service for registration and pathways.

Describe how symptoms affect work, study, caring responsibilities, sleep and daily life. If a previous visit did not address the problem, bring a concise timeline and ask for a follow-up plan. Diagnosis may require more than one appointment; persistent or changing symptoms deserve reassessment even if an initial test was normal.

NICE recommendations provide a basis for discussion in relevant settings, but local services and referral routes can differ. Ask who is responsible for the next step, how results will reach you and what to do if an appointment or investigation is delayed. A private opinion can complement care, but it should include clear handover and access to appropriate follow-up.

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Accessibility and respectful language

People may face obstacles including appointment timing, disability, language, geography, cost, past discrimination or difficulty being believed. These barriers are not evidence that a person's symptoms are less important. Ask for the format and support that would make the visit accessible, such as written information, an interpreter or a longer appointment where available.

NHS England explains the duty to make reasonable adjustments for disabled people, with examples including accessible letters and longer appointments. Explain which barrier you encounter and what adjustment would help. Arrangements and relevant law can differ across the UK, so ask the local service how to request support.

Good care uses the person's name and terms while asking sensitively about relevant organs, treatments and reproductive goals. Sex characteristics, gender identity and hormone therapy do not determine each other. An examination should be explained and consent obtained, with a chaperone offered where appropriate; a patient can ask questions or withdraw consent.

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Checking qualifications and claims

Healthcare titles do not all mean the same thing. The Health and Care Professions Council lists the professions it regulates, including dietitians. The Association for Nutrition maintains a voluntary register of nutritionists; it is not the same as statutory regulation by the HCPC. Ask a practitioner about their training, professional registration, scope of practice and arrangements for referral.

Ask who will prescribe, which regulated product is proposed, how monitoring and side effects are managed and whether the practitioner sells the recommended tests or supplements. A confident explanation and a large number of certificates are not a substitute for evidence, appropriate registration or a clear route for urgent care.

A reasonable plan should make room for questions and a second opinion. It should describe measurable goals, follow-up and what happens if the approach does not help. Beware of pressure to stop necessary treatment, pay for a large package immediately or accept that every symptom has a single unverified cause.

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Chapter 44

Urgent signs and safer next steps

Possible ectopic pregnancy and sudden testicular pain

If you might be pregnant and have a combination of one-sided lower abdominal pain, vaginal bleeding or brown discharge, shoulder-tip pain, or discomfort when passing urine or stool, contact a GP or NHS 111 promptly. This applies even without a positive pregnancy test. An ectopic pregnancy can become an emergency.

Sudden, sharp, intense abdominal pain, severe dizziness or fainting, feeling sick and looking very pale can indicate rupture. Go to A&E or call 999. Tell the team if pregnancy is possible and when symptoms began. Do not wait for an appointment to discuss hormone levels.

Sudden severe pain in a testicle, pain with nausea or abdominal pain, or pain lasting more than an hour or continuing at rest requires immediate assessment at A&E. Testicular torsion is one possible cause and needs rapid treatment. A lump, swelling or a change in shape without sudden severe pain still needs GP assessment.

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After birth and after menopause

After birth, sudden or very heavy bleeding, especially with faintness, dizziness or a racing heart, needs emergency help. NICE also describes urgent postpartum signs including chest pain, shortness of breath, severe headache with visual symptoms, fever or a painful swollen calf. The timing, severity and other symptoms determine the response: call 999 for severe or rapidly worsening symptoms.

Postpartum psychosis is a medical emergency. Sudden confusion, hallucinations, unusual beliefs, mania or rapidly changing mood after birth need immediate help and same-day assessment. Contact a GP, midwife, crisis service or NHS 111 urgently; call 999 or attend A&E if there is immediate danger. Family or friends can help communicate what has changed.

Any vaginal bleeding after menopause needs a GP appointment even if it happened once, is a small amount or you are unsure it is blood. It often has a non-cancer cause, but should be investigated. Bleeding on HRT also needs review according to its timing and pattern; NICE's updated guidance sets out when assessment or referral is indicated.

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Adrenal crisis and fast-changing symptoms

Adrenal crisis is an emergency. A person with known adrenal insufficiency who becomes acutely unwell, particularly with severe weakness, vomiting, collapse or confusion, should follow their emergency steroid plan and seek emergency help immediately. Give prescribed emergency hydrocortisone as instructed and call 999; do not delay while waiting for a cortisol result.

People taking long-term glucocorticoids may also be at risk of adrenal insufficiency. Do not stop treatment abruptly. Ask the prescribing team for sick-day rules, emergency supplies when appropriate and clear instructions for vomiting or serious illness. NICE explains identification, management and safety information.

Rapidly developing or severe androgen-related changes, such as suddenly progressive excess hair growth or virilisation, need prompt clinical evaluation for causes beyond PCOS. New pelvic pain, unexplained bleeding or a marked change in symptoms also warrants assessment. The urgency depends on the whole picture; NHS 111 can help when you are unsure where to turn.

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Chapter 45

Preparing for a useful clinical conversation

Bring the pattern, not a diagnosis to prove

A short timeline can include when symptoms began, frequency, severity, effects on daily life and any relationship with bleeding, medication, sleep, eating, pregnancy or a significant illness. For cyclical symptoms, record both good and difficult days across at least two cycles when possible. A diary supports assessment but does not have to be perfect.

List relevant medicines, contraception, hormone treatment, supplements and doses, including recent changes. Bring previous test results with dates, units and laboratory ranges if available. Mention cycle timing, time of day, pregnancy or breastfeeding where relevant, because these can change interpretation.

Prioritise the one or two concerns that matter most. Ask what could explain them, what else should be considered and which signs need more urgent attention. It is acceptable to say that you want an explanation of the reasoning, especially if a previous assessment felt dismissive.

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Questions about tests and treatment

Before a test, ask: What question will this answer? Does it need a particular cycle day or time of day? Could a medicine, supplement, illness or hormone treatment affect it? What happens if the result is borderline, normal or unexpected? Ask who will explain the result and when.

Before a treatment, ask: What benefit is realistic for my main symptom, how long might it take, what side effects or risks matter for my history, and what alternatives are available? How will we know whether it is working, and what should I do if it is not? If pregnancy or fertility is relevant, include that in the decision.

Request a written plan or note down the agreed next steps. Ask when to follow up, who to contact if results do not arrive and what change should prompt earlier review. If a referral is needed, ask which service will receive it and how information from private and NHS care can be shared with your consent.

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Use knowledge to make decisions together

Guidelines describe evidence for groups of people, while care is chosen for an individual. Age, anatomy, health history, reproductive goals, preferences, affordability and access can all matter. Ask how a recommendation applies to you and where the evidence is uncertain.

An explanation may change as new information arrives. A clinician can treat symptoms while investigating their cause, and a person can seek a second opinion if important questions remain unanswered. Do not wait for a perfect explanation before seeking help for a warning sign.

Hormone literacy means understanding both what a test can reveal and what it cannot. Keep the symptom, the person and the decision in view. The aim is a workable plan that is reviewed over time, with appropriate specialist input when needed.

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Understanding Hormones:A Guide to Hormones, Symptoms and Blood Tests

Contents

First, know when to get help

Life-threatening hormone emergencies

Dangerous high or low glucose

Urgent advice, and how to use this book

Hormones: messages between cells

Chemical messengers and their destinations

Receptors and the shape of a response

Timing, clearance and variation

Feedback loops and endocrine axes

The hypothalamus and pituitary

Primary and central problems

Dynamic tests and treatment sequence

Symptoms, assessment and the first consultation

Patterns are useful, not proof

A timeline and medicine history

Understanding a result and its limits

Pituitary conditions, prolactin and growth hormone

When the pituitary makes too little

Prolactin: one result, several explanations

Growth hormone and acromegaly

Stress physiology and the cortisol rhythm

The stress response has a biological purpose

A rhythm is not a single optimum value

Distress, fatigue and the adrenal fatigue label

Adrenal insufficiency, steroid exposure and crisis

Recognising insufficient cortisol

Morning cortisol in the NICE pathway

Replacement, sick days and preventing crisis

Cortisol excess, aldosterone and adrenal tumours

Cushing syndrome and careful testing

Aldosterone, renin and high blood pressure

Phaeochromocytoma and incidental findings

Insulin, glucagon and the supply of fuel

The pancreatic islets

Resistance and the beta-cell response

The gut and the counter-regulatory response

Diabetes: types, diagnosis and ongoing care

Different mechanisms can produce high glucose

Glucose, HbA1c and classifying diabetes

Treatment is more than a glucose number

Low blood glucose: recognising and investigating a hypo

Why glucose can fall

What to do when a person can swallow safely

Severe episodes and assessment without diabetes

Thyroid physiology, testing and underactivity

The thyroid and its feedback loop

TSH, free T4 and the pituitary exception

Underactive thyroid and levothyroxine

Overactive thyroid and thyroid enlargement

Different paths to excess thyroid hormone

Treatment choices and urgent medicine effects

A lump or enlarged thyroid

Parathyroid hormone, calcium and phosphate

Keeping calcium available

Primary hyperparathyroidism: the NICE pathway

Calcium emergencies and low calcium

Bone health and endocrine fracture risk

Bone is living tissue

Who should have risk assessed?

A plan after assessment

Thirst, vasopressin and sodium balance

How water balance is controlled

AVP deficiency and resistance

Low sodium and desmopressin safety

Medicines, monitoring and shared decisions

What medicines can change

Questions to take to an appointment

Coordinating care and emergency plans

Reproductive hormones across the life course

The brain, pituitary and reproductive organs

Puberty is a transition, not a single event

A changing system needs a changing question

The menstrual cycle in detail

Follicular phase and ovulation

The luteal phase and menstruation

Tracking symptoms without drawing premature conclusions

PMS, PMDD and cyclical symptoms

Recognising the pattern

Understanding Hormones:
A Guide to Hormones, Symptoms and Blood Tests