Irregular Periods Algorithm

Safety

Red Flags — Exclude urgent and malignant causes first

Done

Most irregular bleeding in the reproductive years is anovulatory and benign, but the same complaint can hide an early pregnancy (including ectopic), a cervical or endometrial cancer, or a pituitary lesion. Run through the tiles below before you settle on a benign label, and document that you have done so.

Pregnancy not excluded Any change in bleeding pattern in someone who could be pregnant → Urine hCG first. Positive test with haemodynamic instability, significant pain/bleeding, shoulder-tip pain, syncope, collapse or peritonism → A&E. Positive test with abdominal/pelvic pain, tenderness or cervical motion tenderness → Immediate EPAU / out-of-hours gynaecology. Bleeding but no pain, <6 weeks, no risk factors → clinical assessment ± expectant management with clear safety-netting. Bleeding with pain, ≥6 weeks or uncertain gestation → EPAU; urgency by clinical status (NICE NG126, 2019, updated June 2026)

Postmenopausal bleeding, aged 55 or over Unexplained bleeding more than 12 months after the last period that is not attributable to HRT timing or an identified benign cause → Suspected cancer pathway — NICE NG12 (updated April 2026), rec 1.5.12

Postmenopausal bleeding, under 55 Unexplained and not attributable to HRT → Consider suspected cancer pathway — NICE NG12 (updated April 2026) for endometrial cancer. Bleeding attributable to expected HRT settling → manage via the BMS/NICE HRT pathway, not the standard PMB pathway. Keep PMB separate from reproductive-age AUB

Cervix looks abnormal On speculum the appearance of the cervix is consistent with cervical cancer (friable, ulcerated, mass) → Consider suspected cancer pathway — NICE NG12 (updated April 2026)

Persistent postcoital / intermenstrual bleeding Not a stand-alone NG12 criterion, but needs a speculum, STI tests and a clear plan. Normal cervix + persisting symptoms → Gynaecology referral (local PCB/IMB pathway)

Haemodynamic instability Heavy bleeding with dizziness, syncope, tachycardia or hypotension, or shoulder-tip pain, collapse or peritonism with possible pregnancy → 999 (haemorrhage or ruptured ectopic)

Persistent intermenstrual or irregular bleeding Requires examination and a clear investigation plan. Consider urgent gynaecological assessment with endometrial risk factors (infrequent heavy bleeding with obesity or PCOS, tamoxifen), persistent symptoms, failed treatment, heavy bleeding, or findings suggestive of structural/endometrial pathology → Local symptomatic gynaecology pathway. Age alone is not an NG12 referral criterion

Galactorrhoea + amenorrhoea Check prolactin first (repeat if mildly raised); review antipsychotics, metoclopramide, domperidone, opioids and other relevant drugs; check TSH; consider macroprolactin per local laboratory practice. Persistent significant elevation, visual symptoms or headache → Endocrinology advice ± pituitary imaging through the appropriate pathway

Visual-field loss, neurological deficit or severe headache + raised prolactin/amenorrhoea Bitemporal field loss suggests a pituitary macroadenoma pressing on the chiasm → Same-day specialist assessment. A mild isolated prolactin elevation does not automatically require same-day review

Rapid virilisation Deepening voice, clitoromegaly, fast-progressing hirsutism over months → suspect an androgen-secreting tumour → Urgent endocrinology

Persistent symptoms suggestive of ovarian cancer Persistent bloating, early satiety, pelvic pain or urinary frequency. Aged ≥40: CA125 with age-specific NG12 (updated April 2026) thresholds (40–49 ≥35; 50–59 ≥31; 60–69 ≥24; 70–79 ≥25; ≥80 ≥31 IU/mL) and Urgent abdominal/pelvic USS according to age and result. Aged ≤39: do not use CA125 alone — consider urgent USS. CA125 is not diagnostic; a normal result does not exclude ovarian cancer. Ascites or a pelvic/abdominal mass not obviously due to fibroids → suspected cancer pathway without waiting for CA125

Weight loss or low BMI + amenorrhoea Consider an eating disorder or a systemic illness (coeliac disease, thyrotoxicosis, malignancy). Weigh, check bloods and ask directly about restriction and purging. Suspected eating disorder → refer without delay to the age-appropriate community eating-disorder service. Severe malnutrition, dehydration, electrolyte abnormality, bradycardia, hypotension, syncope, hypoglycaemia, arrhythmia or organ compromise → Acute medical assessment. Don't use fixed BMI thresholds alone to judge risk (NICE NG69)

Cancer Research UK ranks uterine cancer as the fourth most common cancer in UK women, and bleeding is usually its first symptom, so the bleeding history is where it gets caught early. The April 2026 update to NICE NG12 kept the suspected cancer pathway for unexplained postmenopausal bleeding at 55 and over, but only where HRT does not explain it. For unscheduled bleeding on HRT the guideline points to British Menopause Society practice. Persistent postcoital bleeding is not an NG12 trigger by itself; a normal-looking cervix with ongoing bleeding still needs a gynaecology assessment through your local pathway. Ectopic pregnancy remains a cause of maternal death in the UK, so any woman who could be pregnant needs an hCG before anything else. A prolactinoma can grow silently until it threatens vision. In an SCA case, say out loud that you are excluding pregnancy and cancer first: examiners mark safety before cleverness.

Diagnose

History — Characterise the menstrual pattern

Done

Pin down the pattern before you order tests. A bleeding diary (paper or app) kept over about 3 cycles turns "irregular" into dates, and often settles the question of whether the problem is infrequent periods, frequent periods, bleeding between periods or heavy periods.

Cycle characterisation

First day of each period, cycle length, days of bleeding, flooding or clots, pain. A normal adult cycle is roughly 21–35 days

Pattern of irregularity

Adults and >3 years post-menarche: infrequent (cycles over 35 days, fewer than 8 periods a year, or any cycle over 90 days); frequent (under 21 days). Adolescents: the first year after menarche is physiologically irregular; 1–3 years post-menarche, cycles <21 or >45 days are abnormal (International PCOS Guideline 2023); absent (no period for 3 months with previously regular cycles, or 6 months with previously irregular ones — a working definition used in practice); intermenstrual (IMB) or postcoital (PCB) bleeding

Onset and triggers

Recent change of contraception, weight change, stress, travel, illness, intensive training, new medicines, recent pregnancy or breastfeeding

Reproductive history

Age at menarche; pregnancies and miscarriages; current contraception and whether pregnancy is wanted now or later — this shapes every treatment choice

Contraception / HRT

Unscheduled bleeding is common in the first 3 months of any hormonal method and with progestogen-only methods (implant, injection, POP). New or persistent bleeding after that deserves assessment (CoSRH CEU guidance on problematic bleeding with hormonal contraception, 2015)

Sexual health

New or multiple partners, condom use, discharge, dyspareunia — chlamydia and gonorrhoea cervicitis commonly cause PCB and IMB

Systemic symptoms

Acne, hirsutism, scalp hair thinning, weight gain (PCOS); heat or cold intolerance, palpitations, fatigue (thyroid); galactorrhoea, headache, visual change (prolactin/pituitary); hot flushes, night sweats (perimenopause, POI)

Eating and exercise

Restriction, purging, rapid weight loss, very high training loads, low energy availability — functional hypothalamic amenorrhoea

Medications

Antipsychotics, metoclopramide and domperidone raise prolactin; anticoagulants and some SSRIs increase bleeding; tamoxifen affects the endometrium

Family history

PCOS, type 2 diabetes, thyroid disease, early menopause (POI), bleeding disorders such as von Willebrand disease, endometrial or bowel cancer (Lynch syndrome)

Ideas, concerns, expectations

Fear of cancer, worry about fertility, embarrassment about hair growth or weight. Ask directly — it changes what the patient wants from the consultation

A bleeding diary converts a vague complaint into data you can act on and gives you a baseline for judging whether treatment works. Contraception is the commonest reason for irregular bleeding in general practice and is easy to overlook if you do not ask about it first. The 2023 International Evidence-based Guideline for PCOS (international; Monash/ESHRE) defines irregular cycles from 3 years after menarche as under 21 or over 35 days, or fewer than 8 cycles a year, and uses wider limits in the first years after menarche, so age since menarche matters. Ask about fertility plans early: someone trying to conceive needs a different plan from someone who wants cycle control and contraception. The sexual history is not optional, because an STI is a treatable cause of postcoital bleeding.

Diagnose

Classification — Identify the aetiology group

Done

Sort the likely cause into one of the groups below. The feature in each row is the one that separates it from its neighbours.

PCOS

Adults need 2 of 3, after excluding other causes: ovulatory dysfunction, clinical or biochemical hyperandrogenism, and polycystic ovarian morphology on ultrasound or an appropriate AMH-based criterion. If irregular cycles and hyperandrogenism are both present, ultrasound is not needed. AMH is not a standalone diagnostic test. Don't use ultrasound or AMH within 8 years of menarche, where both criteria rest on cycles plus hyperandrogenism (International PCOS Guideline, 2023 — international)

Thyroid disease

Hypothyroidism: heavier or irregular periods; hyperthyroidism: lighter, infrequent or absent periods. TSH is cheap and treatable — check it

Hyperprolactinaemia

Galactorrhoea ± headache ± infrequent periods. Separate drug-induced, macroprolactin (a lab artefact) and pituitary adenoma

Premature ovarian insufficiency

Under 40 with infrequent or absent periods and menopausal symptoms, plus raised FSH. NICE NG23 (2015, updated April 2026) asks for raised FSH on 2 samples 4–6 weeks apart — do not diagnose POI from one blood test, and do not routinely use AMH. FSH need not be timed to cycle days 2–5. Interpretation may be unreliable on hormonal contraception or HRT — seek specialist advice

Perimenopause

Aged 45 or over with a changing cycle ± vasomotor symptoms: diagnose clinically without FSH (NICE NG23)

Functional hypothalamic amenorrhoea

Low weight, restriction, heavy exercise or stress; low or low-normal LH/FSH with low oestradiol. A diagnosis of exclusion

Structural (PALM: polyp, adenomyosis, leiomyoma, malignancy/hyperplasia)

More likely with IMB, PCB, heavy bleeding, an enlarged or irregular uterus or pelvic pain. Ultrasound or outpatient hysteroscopy according to symptoms and risk (NICE NG88). PALM-COEIN is a classification framework, not a diagnostic test

Cervical / infective

Cervicitis (chlamydia, gonorrhoea), ectropion, cervical polyp — suggested by PCB and discharge

Physiological

First 1–3 years after menarche, postpartum, breastfeeding, perimenopause — often settles, but only after red flags are excluded

Iatrogenic

Hormonal contraception, antipsychotics, anticoagulants, tamoxifen, chemotherapy or pelvic radiotherapy

The 2023 International PCOS Guideline puts prevalence at about 10–13% of women of reproductive age, making PCOS the commonest endocrine cause of infrequent periods. The guideline now lets AMH stand in for ultrasound in adults, but not in adolescents, where multi-follicular ovaries are normal. Premature ovarian insufficiency is easy to mislabel as stress or PCOS. Missing it leaves a young woman without oestrogen, which harms bone and cardiovascular health, so FSH belongs in the work-up of anyone under 40 with prolonged absent periods. Classifying the cause tells you where the patient goes next: primary care for most PCOS, thyroid and drug causes; gynaecology for structural disease; endocrinology for pituitary or androgen-secreting lesions; and a specialist service for POI.

Diagnose

Examination — Focused clinical assessment

Done

Offer a chaperone and explain why each part matters. Examine before you investigate — NICE NG88 (heavy menstrual bleeding, 2018, updated July 2026) asks for a physical examination before investigations or LNG-IUS fitting.

BMI, waist and BP

Low BMI (<18.5): hypothalamic amenorrhoea, eating disorder. Raised BMI and waist: PCOS and insulin resistance. BP as part of cardiometabolic risk

Skin / hair

Hirsutism — the key finding is new or progressive terminal hair growth in a male-pattern distribution (modified Ferriman–Gallwey scoring is supportive, not absolute: thresholds vary with ethnicity, hair-removal practices and local reference standards; use biochemical testing when clinical assessment is unclear or virilisation is present), acne, scalp hair loss, acanthosis nigricans (insulin resistance), purple striae and proximal weakness (Cushing's)

Thyroid

If clinically indicated: goitre, tremor, tachycardia, lid lag (hyper); bradycardia, dry skin, slow-relaxing reflexes (hypo)

Breasts

Only if galactorrhoea is reported: bilateral milky discharge points to prolactin. Unilateral or blood-stained discharge is a breast-pathway question

Visual fields

Confrontation fields if prolactin is raised or there is headache — look for bitemporal loss

Abdomen

Palpable pelvic mass or enlarged uterus (fibroids); signs of virilisation (clitoromegaly) suggest a tumour

Speculum

Use for PCB, persistent IMB, abnormal discharge, suspected cervical lesion or cervicitis, and persistent unexplained bleeding. Look at the cervix itself: an ectropion, polyp or cervicitis versus a suspicious, friable or ulcerated lesion

Bimanual

When there is pelvic pain, suspected pelvic mass, uterine enlargement, adnexal symptoms or cervical motion tenderness: uterine size and contour, adnexal masses, cervical excitation or adnexal tenderness (pelvic infection, ectopic). Not routinely needed for isolated oligomenorrhoea

Swabs

NAAT for chlamydia and gonorrhoea (vulvovaginal or endocervical) when there is PCB, IMB or any STI risk

Cervical screening status

Check the history and make sure routine screening is up to date. Screening is not a diagnostic test for symptoms: a normal recent result does not explain PCB, and a screening sample must not delay symptomatic referral

BMI is often the single most informative finding: it points you towards PCOS at one end and hypothalamic amenorrhoea or an eating disorder at the other. Hypothalamic amenorrhoea is diagnosed clinically and confirmed by the pattern of low oestradiol without raised FSH. Virilisation (clitoromegaly, a deepening voice, rapidly worsening hirsutism) is uncommon but suggests an ovarian or adrenal androgen-secreting tumour and needs urgent endocrinology input. Cervical screening is designed for people without symptoms. A symptomatic cervix needs to be looked at, swabbed for infection and referred on its appearance or on persistent symptoms, not "smeared and reassured". A documented speculum examination is also the thing examiners and medicolegal reviewers look for.

Diagnose

Investigations — Targeted tests and imaging

Done

Order tests to answer specific questions. A standard "hormone profile" sent on a random day is often uninterpretable.

Infrequent or absent periods — targeted tests

Urine hCG where pregnancy is possible. TSH if thyroid disease is possible or the cause is unclear. Prolactin if amenorrhoea, galactorrhoea, headache, visual symptoms or relevant medication. FSH ± LH only where POI, hypothalamic/pituitary disease or ovarian failure is suspected. Oestradiol is not routinely required to diagnose PCOS or POI. FBC if heavy/prolonged bleeding or anaemia possible; STI NAAT where indicated. Check medication and hormonal contraception before interpreting results — FSH cannot diagnose menopause in people using combined hormonal contraception or high-dose progestogen

PCOS work-up

Total testosterone + calculated free testosterone or free androgen index, SHBG; consider DHEAS if testosterone is not raised but androgen excess remains concerning. Exclude pregnancy, thyroid disease, hyperprolactinaemia and non-classical CAH where clinically indicated. Androgen results are unreliable on combined hormonal contraception. Assess glycaemic status at diagnosis with HbA1c or fasting glucose (an OGTT is preferred in higher-risk women per the International PCOS Guideline 2023), plus Lipids. Ultrasound or AMH is not needed when adult PCOS is diagnosed on irregular cycles plus hyperandrogenism; AMH is not a standalone test and is not used to diagnose PCOS in adolescents

Suspected POI

FSH on two samples 4–6 weeks apart (NICE NG23) — need not be timed to cycle days 2–5; do not diagnose from one test; do not routinely use AMH. On hormonal contraception or HRT, interpretation may be unreliable — seek specialist advice. Once confirmed, specialist-led assessment may include genetic and autoimmune investigations depending on whether POI is spontaneous, iatrogenic or syndrome-associated — not routine GP tests

Androgen excess

Markedly raised testosterone (well above the lab's female reference range) or rapid virilisation → DHEAS and 17-OHP (non-classic congenital adrenal hyperplasia) and urgent endocrinology

Raised prolactin

Repeat, avoiding stress and recent breast stimulation; consider macroprolactin according to local laboratory practice; review antipsychotics, metoclopramide, domperidone, opioids and other relevant drugs; check TSH (hypothyroidism raises prolactin). Persistent significant elevation, visual symptoms or headache → endocrinology advice and pituitary imaging through the appropriate pathway. No pituitary MRI for a single mildly raised prolactin before common causes are excluded

Structural pathology

Pelvic ultrasound (TVUSS) for suspected fibroids, polyps or adenomyosis, a pelvic mass, or PCB/IMB with a normal cervix, per local pathway. NICE NG88 recommends outpatient hysteroscopy where symptoms suggest polyps, submucosal fibroids or endometrial pathology, with any endometrial biopsy taken at hysteroscopy rather than blind biopsy. Routine pelvic ultrasound is not required for isolated oligomenorrhoea without heavy, intermenstrual or postcoital bleeding unless the diagnosis is unclear or there are structural symptoms

Bleeding / anaemia

FBC for anyone with heavy or prolonged bleeding (NICE NG88). Consider a coagulation screen and von Willebrand testing if heavy since menarche or with a personal or family bleeding history

Ovulation (fertility)

Only when assessing ovulation in a fertility context — not routine for irregular periods. Progesterone approximately 7 days before the expected next period, not automatically on day 21 (about day 21 of a 28-day cycle, about day 28 of a 35-day cycle), repeated weekly until the next period if cycles are prolonged and irregular (NICE NG257 Fertility problems, March 2026; replaced CG156)

Not routine in primary care

MRI pelvis; blind endometrial biopsy (sampling is gynaecology-led, at hysteroscopy); blanket "hormone profiles"; pituitary MRI before prolactin has been confirmed and macroprolactin excluded

TSH and prolactin are cheap, treatable and often missed, so check them when clinically indicated in the work-up for infrequent or absent periods. Macroprolactin is a large, biologically inactive complex that raises the lab result without causing disease. Screening for it saves unnecessary MRI scans and referrals. POI is confirmed by persistently raised FSH, and the diagnosis has major implications for bone, heart and fertility, so it goes to a specialist once confirmed. Endometrial sampling is a gynaecology procedure, taken at diagnostic hysteroscopy rather than as a blind primary-care biopsy. Testosterone assays differ between laboratories, so the trigger for urgent endocrinology is a result markedly above your lab's female reference range or clinical virilisation, not a single universal number. In the SCA, explain in plain language why each blood test is being done and how the results will reach the patient.

Refer

Referral Criteria — Gynaecology, Endocrinology, and beyond

Done

Suspected cancer pathway (NICE NG12, updated April 2026)

Refer: aged 55 or over with unexplained postmenopausal bleeding not attributable to HRT (rec 1.5.12). Consider: under 55 with unexplained postmenopausal bleeding not attributable to HRT; cervix whose appearance is consistent with cervical cancer. Ovarian: ascites or a pelvic/abdominal mass not obviously due to fibroids → refer without waiting for CA125; persistent symptoms aged ≥40 → CA125 (age-specific thresholds) + urgent USS; aged ≤39 → consider urgent USS (CA125 alone not used)

Same-day

Haemodynamic compromise, shoulder-tip pain, syncope/collapse or peritonism → A&E. Positive hCG with pain, pelvic tenderness or cervical motion tenderness → immediate EPAU / out-of-hours gynaecology; positive hCG with bleeding and pain, ≥6 weeks or uncertain gestation → EPAU, urgency by clinical status (NICE NG126); acute abdomen; new visual-field loss or neurological deficit with suspected pituitary lesion → same-day specialist assessment

Urgent gynaecology

Persistent PCB or IMB with a normal-looking cervix and negative STI tests; persistent irregular bleeding; infrequent heavy bleeding with obesity or PCOS; tamoxifen use; failed medical treatment; abnormal cervix; pelvic mass or enlarged uterus; significant anaemia or ongoing heavy bleeding; ultrasound showing a thickened or irregular endometrium (per the local symptomatic gynaecology pathway)

Specialist POI / menopause service

Confirmed POI — hormone replacement, bone and cardiovascular protection, fertility and genetic counselling (NICE NG23)

Routine gynaecology

Fibroids or polyps on imaging, suspected adenomyosis or endometriosis, heavy bleeding not controlled by first-line treatment (NICE NG88)

Endocrinology

Confirmed hyperprolactinaemia with no drug or macroprolactin explanation; markedly raised androgens or virilisation (urgent); suspected Cushing's or non-classic CAH

Fertility services

Anovulation in someone trying to conceive — referral based on infertility duration, age, ovulatory dysfunction and other risk factors (NICE NG257, 2026); not every person with PCOS and irregular periods needs immediate referral

Eating disorder service

Suspected eating disorder — refer without delay to the age-appropriate community eating-disorder service (NICE NG69, 2017); severe physical compromise → acute medical assessment; don't rely on BMI alone to judge risk

Primary care manage

PCOS with no red flags; hypothyroidism; drug-induced hyperprolactinaemia (with prescriber input); perimenopause; contraception-related bleeding after assessment

Local pathway

Use local symptomatic gynaecology, EPAU, endocrinology, fertility and eating-disorder referral pathways

NG12 recommendation 1.5.12, as amended in April 2026, is a "refer" for unexplained postmenopausal bleeding at 55 and over. The under-55 and cervix criteria are "consider", which leaves room for judgement but still means documenting your reasoning. POI needs specialist input because untreated oestrogen deficiency at a young age raises the risk of osteoporosis and cardiovascular disease; NICE NG23 recommends hormone treatment, either HRT or a combined hormonal contraceptive, unless contraindicated. Confirm a raised prolactin before referring: a single high value after a difficult venepuncture, or one due to macroprolactin, generates avoidable scans. The endocrinologist decides whether pituitary imaging is needed and when.

Treat

Treatment — Cause-directed and fertility-aware management

Done

PCOS (no pregnancy wish)

Combined hormonal contraception 1st line

Provides contraception, regulates cycles, reduces the risk from prolonged anovulatory endometrial exposure and may improve acne and hirsutism — it does not cure PCOS (International PCOS Guideline 2023). Check UKMEC before prescribing, especially BMI, BP and migraine with aura. Dose and choice per BNF.

PCOS (trying to conceive)

Fertility assessment ± referral

Refer according to infertility duration, age, ovulatory dysfunction and other risk factors. The International PCOS Guideline (2023) names letrozole as first-line pharmacological ovulation induction. It is unlicensed for this use in the UK and specialist-initiated. Advise folic acid, and weight optimisation if BMI is raised.

Primary hypothyroidism

Levothyroxine

Confirm the diagnosis and severity with TSH and free T4, then treat according to NICE NG145 (overt vs subclinical). Starting dose depends on age, cardiovascular disease and severity: about 1.6 micrograms/kg/day under 65 without CVD; 25–50 micrograms/day with titration at 65+ or with CVD. Review TSH after an appropriate interval and titrate.

Drug-induced hyperprolactinaemia

Medication review

Switch or reduce the culprit only with the prescriber (psychiatry for antipsychotics). Never stop an antipsychotic abruptly. If amenorrhoea persists, consider oestrogen replacement for bone health.

Functional hypothalamic amenorrhoea

Restore energy availability

Exclude pregnancy; assess for eating disorder, low energy availability and excessive exercise; FBC, U&E, glucose, liver profile, TSH, prolactin, LH/FSH and oestradiol where clinically indicated; bone-health assessment if amenorrhoea is prolonged; early eating-disorder referral where relevant. Weight restoration or menstrual return is not the only treatment goal.

Perimenopause / POI

HRT or combined hormonal contraception

For POI, offer sex-steroid replacement until at least the average age of natural menopause unless contraindicated, with specialist input and contraception if pregnancy is not desired (NICE NG23). In perimenopause, remember contraception is still needed.

Bleeding on hormonal contraception

Assess, then adjust

Once pregnancy, STI and cervical pathology have been excluded, options depend on the method (CoSRH CEU guidance, 2015). Many settle after 3 months.

Endometrial protectionIn prolonged untreated anovulation, ensure endometrial protection after pregnancy has been excluded. Options include a combined hormonal contraceptive, an LNG-IUS or an intermittent progestogen regimen (e.g. a withdrawal bleed at least every 3–4 months — RCOG Green-top Guideline 33, 2014). Choice, dose and duration per product information, local formulary and specialist guidance, particularly where bleeding is new, heavy or persistent. Do not use a withdrawal bleed to reassure a patient with unexplained abnormal bleeding — it still needs examination and investigation

Metformin (PCOS)May be considered for metabolic outcomes in adults with PCOS, especially where BMI is ≥25, alongside lifestyle advice (International PCOS Guideline 2023) — not primarily a treatment for irregular bleeding and not required for everyone with BMI ≥25. Off-label for PCOS in the UK; start low and titrate; monitor tolerance and renal function per product information/local formulary

HirsutismCombined contraception first, with cosmetic hair removal alongside; specialist-led anti-androgens need reliable contraception because of the risk to a male fetus

Next steps: see PCOS · Menopause and HRT · Contraception · Hypothyroidism · Eating disorders

Months without a period mean months of oestrogen without progesterone on the endometrium. In prolonged untreated anovulation, endometrial protection (CHC, LNG-IUS or an intermittent progestogen; RCOG Green-top Guideline 33 describes a withdrawal bleed at least every 3–4 months) is offered after pregnancy and abnormal pathology have been excluded. A meta-analysis (Barry et al., Hum Reprod Update 2014) found women with PCOS had about 2.8 times the odds of endometrial cancer. Doses are given only where a primary source states them (NICE NG145 for levothyroxine); otherwise check the SPC and your local formulary. In the SCA, check the plan against the patient's goal (cycle control, contraception, fertility or hair) and state the risks you are protecting against.

Lifestyle

Non-Pharmacological Interventions — The foundation of PCOS and hypothalamic care

Done

Weight management (PCOS) With excess weight, a 5–10% loss within 6 months brings meaningful clinical improvements (International PCOS Guideline 2023). Any healthy eating pattern that is sustainable is acceptable; avoid weight stigma

Physical activity Aim for at least 150 minutes of moderate activity a week plus muscle strengthening on 2 days (UK Chief Medical Officers' physical activity guidelines, 2019). Activity helps insulin resistance even without weight loss

Energy availability In hypothalamic amenorrhoea, periods usually return when energy intake matches expenditure: restore weight, reduce training load, address stress. Coaches and sports medicine can help athletes. Weight restoration or menstrual return is not the only goal — address eating-disorder risk and bone health too

Eating disorders Ask sensitively and early. If suspected, refer without delay to the age-appropriate community eating-disorder service. Severe malnutrition, dehydration, electrolyte abnormality, bradycardia, hypotension, syncope, hypoglycaemia, arrhythmia or organ compromise → acute medical assessment (NICE NG69). Avoid fixed BMI thresholds as the sole basis for risk assessment

Bleeding diary Record each bleeding day on paper or an app for 3 months. Bring it to review to judge response

Bone health (POI, hypothalamic amenorrhoea) Weight-bearing exercise, adequate dietary calcium, and vitamin D per UK public health advice (10 micrograms daily). DXA as advised by the specialist

Alcohol and smoking Keep alcohol within the UK CMO low-risk limit of 14 units a week spread over 3 or more days; offer stop-smoking support — it improves cardiometabolic risk in PCOS

Emotional wellbeing PCOS is linked with higher rates of anxiety, depression and body-image distress; the International PCOS Guideline 2023 advises screening for them. Offer support or talking therapy

Lifestyle change is the foundation of PCOS care and is recommended for everyone with PCOS, whatever their weight, because insulin resistance drives much of the hyperandrogenism and anovulation. In hypothalamic amenorrhoea, adding hormones does not fix the underlying energy deficit: restoring energy availability does. Lifestyle discussions go better when you acknowledge the difficulty. In an SCA, a shared, specific and achievable goal scores better than a lecture.

Safety

Follow-Up and Safety-Netting

Done

Results (1–2 weeks)

Agree how results will be given. Act on hCG, prolactin, TSH and FSH; arrange the repeat FSH or prolactin if needed

3 months

Review the bleeding diary, response to treatment, side effects, weight and mood; confirm endometrial protection is in place

Annual (PCOS)

Weight, BP, glycaemic status and lipids as advised by the International PCOS Guideline 2023; review contraception and mood

POI

Shared care with the specialist: HRT review, bone health, cardiovascular risk

999 now

Heavy bleeding with fainting, chest pain, breathlessness or collapse

Same day

Positive pregnancy test with pain or bleeding (ectopic); new visual-field loss, neurological symptoms or severe headache with raised prolactin/absent periods

Urgent reassessment

Persistent bleeding after sex or between periods; any postmenopausal bleeding; bleeding that becomes heavier or continuous; suspicious cervical lesion; new pelvic mass, severe pelvic pain or bloating; rapidly progressive virilisation

Re-refer if

Timing depends on diagnosis, treatment, bleeding severity, risk factors and adequacy of investigation — escalate earlier if bleeding is heavy, persistent, postcoital, with a suspicious cervix or with pelvic symptoms; wishing to conceive; imaging shows a new or thickened endometrium

Safety-net script"Most irregular periods are caused by hormone changes rather than anything serious. But if you bleed after sex, between periods, or at all once your periods have stopped for a year, please book to see us again — don't wait for your review. If you ever feel faint with heavy bleeding, or have strong tummy pain and could be pregnant, call 999 or go to A&E."

DocumentationRecord hCG result, speculum findings, the red flags you asked about, the plan for endometrial protection and the safety-net advice given

PCOS carries a lifelong raised risk of type 2 diabetes and cardiometabolic disease, so the International PCOS Guideline 2023 advises regular checks of weight, BP and glycaemic status. Endometrial protection is the step most often lost at follow-up when periods stay infrequent, so check it at every review. People with POI need long-term hormone treatment and review. Stopping at the average menopausal age is a shared decision with the specialist. A worded safety-net that names specific symptoms (bleeding after sex, between periods or after the menopause) is easier for patients to act on than "come back if worse".