Amenorrhoea
Red Flags — the serious causes and consequences
| Red flag | Why it matters | Action |
|---|---|---|
| Hyperprolactinaemia with headache / visual field defect | Pituitary macroadenoma compressing the optic chiasm — risk to vision. | Same-day endocrine/emergency assessment (specialist-directed MRI pituitary); visual field testing |
| Virilisation / rapid androgen rise (deep voice, clitoromegaly, rapid hirsutism) | Androgen-secreting ovarian/adrenal tumour or non-classical CAH. | Urgent androgens (testosterone, DHEAS, 17-OHP); endocrine/gynae referral |
| Premature ovarian insufficiency (<40, raised FSH) | Long-term bone/cardiovascular risk and significant fertility/psychological impact. | Repeat FSH; HRT to ~51; cause work-up; fertility counselling; gynae/endocrine |
| Eating disorder behind hypothalamic amenorrhoea | Serious morbidity/mortality; amenorrhoea may be the presenting sign. | Sensitive assessment; eating-disorder service; don't mask with the pill |
| Prolonged hypo-oestrogenism + prior fragility/stress fracture | Low bone density and fracture risk (female athlete triad / RED-S). | Address energy balance; DXA; calcium/vitamin D; specialist input |
| Primary amenorrhoea with absent secondary sexual characteristics / dysmorphic features | Turner's syndrome, structural/outflow anomaly, or other genetic cause. | Examination, imaging, karyotype; paediatric/gynae/endocrine referral |
🏃 Performance & bones
Frame energy balance around her goals — under-fuelling harms performance and bones.
"Training hard while under-fuelling actually works against you — it weakens bones (which is why you got that stress fracture) and limits performance. Getting your energy balance right will help your running, not hinder it."🍽️ Eating, sensitively
Screen for disordered eating without accusation.
"Can I ask a bit about food — not to judge, but because how we fuel matters so much for this. How do you feel about eating and your body at the moment?"💊 Not just the pill
Explain why the pill alone isn't the fix here.
"It's tempting to just start the pill to bring periods back, but that can mask what's going on and doesn't fully protect your bones. The real fix is restoring your body's energy balance."👶 Fertility honestly
Reassure that this is usually reversible while taking concerns seriously.
"The good news is this type is usually reversible — when your body's better fuelled, periods and fertility typically return. If you ever have trouble down the line, there's plenty of help."- Not doing a pregnancy test
- Not localising along the HPO axis / not ordering the core panel
- Missing the energy-availability/eating-disorder issue and bone risk
- Reflexively prescribing the pill to "fix" it
Days
Don't delay- Pituitary tumour signsVisual field defect ± headache + high prolactin → same-day endocrine/emergency assessment
- Rapid virilisation?androgen-secreting tumour → urgent referral
- Severe eating disorder / very low BMISame-day medical risk assessment (MEED); eating-disorder service
Weeks
Specialist- POI (<40, raised FSH ×2)HRT, cause work-up, gynae/endocrine
- Primary amenorrhoeaExamination, imaging, karyotype; specialist
- Hyperprolactinaemia (no red flags)Confirm, exclude drugs; endocrine
Primary care work-up
Common causes- Functional hypothalamic amenorrhoeaEnergy balance; eating screen; bone protection
- PCOSLifestyle, symptom & endometrial management
- Thyroid / drug-inducedTreat cause; review medication
- Missing pituitary/virilisation red flags
- Not recognising POI's need for timely HRT
- Not documenting BMI; missing androgen/galactorrhoea signs
- Pelvic exam without consent/chaperone or when not indicated
- Skipping the pregnancy test
- Not knowing how the panel localises the axis
- Ignoring bone assessment in a hypo-oestrogenic patient with a stress fracture
🚩 The discipline — localise, and don't forget the bones
Reasoning by HPO level turns a long differential into a clear answer: pregnancy excluded, then FSH/oestradiol (ovary), prolactin (pituitary), androgens (PCOS), TSH (thyroid). For Sophie the formulation is functional hypothalamic amenorrhoea from low energy availability — low oestradiol with low/normal gonadotrophins — within a female-athlete-triad picture whose prior stress fracture signals low bone density. The treatment is restoring energy balance (not the pill), with eating-disorder screening and active bone protection.
- Not localising the cause from the panel
- Labelling without flagging the bone/oestrogen consequence
- Not referring POI for HRT/work-up
- Not involving eating-disorder/dietetic support when indicated
Validate — name what she came for
She came because her mum insisted, feels well, and wants reassurance. She also half-expects to be told to stop running. Naming both expectations out loud stops her feeling ambushed, and shows you have heard that running is central to who she is. It is also honest to say that much of what she hopes is true: this is very likely a reversible, non-dangerous cause.
"You came in hoping I'd say this is nothing to worry about — and I suspect you're also bracing yourself for me to tell you to stop running. I'm not going to do that. But I don't want to just say 'it's fine' either, because your body is giving us a signal that's worth listening to."Explain — share the reasoning in her terms
Link the three things she has not connected: the missing periods, the fuelling, and last year's stress fracture. Explain that the brain turns the ovaries down when energy intake does not cover training, so oestrogen falls; oestrogen is one of the main hormones protecting bone, which is why the fracture matters. Explain why the pill is not the fix: it produces a monthly bleed but does not correct the energy deficit, may not protect bone, and hides whether her own cycle has come back (Endocrine Society FHA guideline, 2017).
"When your body isn't getting enough fuel for the training you're doing, the brain switches off the hormones that drive periods to save energy. Low oestrogen also weakens bone — I think that's part of why you had that stress fracture. A pill would give you a bleed, but it wouldn't fix the fuel gap and it would hide whether your own cycle has come back."Negotiate — something concrete today
She should leave with a plan that protects her running: a pregnancy test and blood panel today, a DXA scan, dietitian and sports-medicine referral, a sensitive eating screen, and a follow-up date. Negotiate the smallest effective change first — for example adding fuel around training and building in a rest day — rather than an ultimatum on mileage. Agree what would make you both change the plan, such as further weight loss or a new bone injury.
"Here's what I'd suggest: bloods and a pregnancy test today, a bone density scan, and I'd like you to see a sports dietitian who works with runners. The aim is to get you fuelled for the training you want to do. Let's review in about six weeks with the results — does that feel doable?"The hypothalamus reads low energy availability as a threat and slows GnRH pulses. LH and FSH fall, the ovaries stop maturing follicles, and oestradiol drops. Leptin, insulin and thyroid hormones fall and cortisol rises, all of which further suppress the axis and harm bone. Restoring available energy reverses this — often before much weight is regained.
Referral to a sports or specialist dietitian. Regular meals and snacks around training, especially carbohydrate before and after sessions; no training fasted. Avoid calorie counting in someone with restrictive traits. Recovery of menses commonly takes months after fuelling improves — say so at the start so she does not give up.
Energy availability is intake minus exercise expenditure. Cutting volume a little is often easier than eating much more, and reduces load on bone that is already under-mineralised. Bone stress injuries in amenorrhoeic runners tend to occur at trabecular-rich sites (pelvis, femoral neck, sacrum), which heal slowly and matter more.
Sports-medicine input using the IOC REDs CAT2 traffic-light system to guide participation. Agree a concrete plan (e.g. one extra rest day, a reduced long run) rather than "do less". Any new bone pain means stop and be assessed — do not run through it.
Oestrogen restrains bone resorption; undernutrition also reduces bone formation. Young women accrue most of their peak bone mass by their late twenties, so a deficit now may be permanent. Calcium and vitamin D are necessary but not sufficient — they do not replace oestrogen or energy.
Dietary calcium first (dairy or fortified alternatives); vitamin D supplement per UK public health advice, higher if deficient. Stop smoking; keep alcohol low. Bisphosphonates are not routine in young women and are specialist-only (they persist in bone and are a concern before pregnancy).
Stress activates the hypothalamic–pituitary–adrenal axis; cortisol and CRH suppress GnRH directly. Perfectionism and food rules keep the energy deficit going even when the athlete "knows" she should eat more. Changing the thinking changes the behaviour.
The Endocrine Society guideline suggests CBT for FHA. Screen with SCOFF; if an eating disorder is suspected, refer to the community eating disorders service straight away (NICE NG69) rather than waiting for dietetics to fail. Consider NHS Talking Therapies for stress and anxiety.
The return of a spontaneous period is the best biomarker of recovered energy availability — but only if she is not on a combined pill, which produces withdrawal bleeds regardless. Tracking also shows whether training blocks or stressful periods set her back.
Any app or diary: bleeding days, training load, rest days, injuries, mood. Bring it to reviews. Weigh in clinic (not at home) if weighing is triggering; blind weighing is acceptable where agreed.
Insulin resistance drives ovarian androgen production and anovulation. Modest weight loss in those with excess weight improves cycles, ovulation, hirsutism and metabolic risk; physical activity improves insulin sensitivity even without weight change.
A healthy, sustainable eating pattern — no single "PCOS diet" is better. Screen mood and disordered eating before any weight conversation; weight stigma harms. Glycaemic screening at diagnosis (75 g OGTT preferred), lipids and BP, as in the site PCOS protocol.
Step 1: energy, training and psychological support (7C). No drug.
- Step 2, only if periods have not returned after a fair trial of nutritional, psychological and exercise change: the Endocrine Society (2017) suggests short-term transdermal 17β-estradiol with cyclical oral progestogen, not a combined pill or ethinylestradiol. Specialist-guided; doses per SPC/specialist.
- The Endocrine Society advises against the COCP just to bring back bleeding or improve bone density. If she chooses a COCP for contraception, explain that it masks whether her own periods have come back and that bone loss may continue while the energy deficit persists.
- Under-18s with anorexia nervosa: do not routinely offer oral or transdermal oestrogen for low bone density; get specialist advice before any hormonal treatment (NICE NG69).
- Contraception during recovery: she can ovulate before her first period. Offer a method that does not depend on cycle tracking. Depot medroxyprogesterone is best avoided when bone density is already a concern because it lowers BMD (MHRA advice; CoSRH).
Lifestyle for all; then by what matters to her now (International PCOS Guideline 2023; site PCOS protocol)
- Cycles and hirsutism: the COCP is first-line after checking UKMEC. Lower ethinylestradiol doses are preferred. Co-cyprindiol is second-line because of VTE risk.
- Endometrial protection if COCP unsuitable: a cyclical progestogen to cause a withdrawal bleed at least every 3–4 months, or an LNG-IUS (RCOG GTG 33).
- No bleed for more than 3–4 months: pregnancy test, then provide progestogen exposure or another endometrial-protection strategy. Routine endometrial ultrasound is not recommended solely for infrequent periods; investigate abnormal bleeding, failed protection or concerning features via the local gynaecology pathway.
- Metabolic: metformin alongside lifestyle, with the best evidence at BMI ≥25 (off-label).
- Fertility: refer. Letrozole is first-line ovulation induction and is specialist-initiated.
Sex-steroid replacement until at least the average age of natural menopause (NICE NG23; ESHRE POI 2024)
- NICE NG23: offer HRT or a combined hormonal contraceptive unless contraindicated. It is given for bone, cardiovascular and symptom protection, not just hot flushes. Current evidence suggests its risks are not raised above those of women of the same age with normal ovarian function, because it replaces hormones they would otherwise have.
- ESHRE 2024 prefers 17β-estradiol to ethinylestradiol for replacement. Younger women often need higher oestrogen doses than typical menopause starting doses. A woman with a uterus always needs a progestogen (or an LNG-IUS). Doses per SPC/specialist.
- HRT is not contraception. A minority conceive spontaneously, so discuss contraception if pregnancy is not wanted. A COCP gives contraception and replacement together.
- Refer to a specialist (menopause/reproductive endocrine) for confirmation of the cause, fertility counselling (donor-egg IVF is the most effective route to pregnancy) and a DXA plan.
- Screen for mass effect first: visual fields, headache, cranial nerve palsy. A new visual field defect with a raised prolactin needs same-day specialist/emergency assessment. A thunderclap headache in someone with a known adenoma is pituitary apoplexy: 999, giving hydrocortisone 100 mg parenterally if adrenal insufficiency is suspected or she is unstable, without delaying transfer.
- Repeat properly: rested sample, preferably at least 2 hours after waking; fasting is not required, and a cannula only if venepuncture stress is suspected. Check TSH, hCG, U&E, and ask for PEG precipitation for macroprolactin in a mildly raised, asymptomatic result.
- Drug-induced: discuss with the prescriber. Never stop or switch an antipsychotic without the psychiatric team. If prolactin stays raised after an appropriate medication review, seek endocrine advice ± MRI.
- Endocrine advice ± MRI pituitary if the rise is persistent and unexplained, at any level with visual, neurological or pituitary symptoms or hypogonadism, or if markedly raised (particularly >2000–2500 mIU/L) without a convincing drug cause — not solely because a fixed threshold is exceeded.
- Prolactinoma: cabergoline is first-line and specialist-initiated.
- The COCP as the "treatment" for hypothalamic amenorrhoea. It produces withdrawal bleeds, hides recovery and does not fix the energy deficit (Endocrine Society 2017).
- Any hormone before pregnancy is excluded, or before a primary amenorrhoea work-up. Starting a pill in a 16-year-old with no periods can delay the diagnosis of Turner syndrome or an outflow anomaly.
- A COCP for hirsutism before a tumour is excluded. Rapid virilisation or testosterone >4 nmol/L needs endocrinology first (site PCOS protocol).
- Unopposed oestrogen in a woman with a uterus. Always add a progestogen or LNG-IUS.
- Levothyroxine for a low T3 in someone starving. Sick euthyroid is adaptive and resolves with refeeding (site eating-disorder protocol).
- Bisphosphonates in a young woman without specialist advice. They persist in bone and raise concerns for future pregnancy.
- Cabergoline started before macroprolactin, drugs and hypothyroidism are excluded, or for a stalk-compression mass.
"This replaces the hormone your ovaries would normally make at your age. It isn't the same as menopause HRT for an older woman — it gives you the levels you'd naturally have, to protect your bones and heart. It isn't contraception."
In POI, say "replacement, not treatment". The risks quoted for HRT in women over 50 do not apply when the aim is to restore normal levels in a woman under 40. For FHA, hormone therapy is second-line after energy restoration and is not a reason to skip the dietitian.
"The bleed you get in the pill-free week is a withdrawal bleed caused by the pill, not a natural period. It won't tell us whether your own cycle has recovered."
The key SCA discrimination is that the COCP is right for PCOS and wrong as the sole treatment for FHA. Name the reason in both cases.
"Without regular periods the womb lining can build up over time. A short course of this tablet every few months lets it shed safely, like a reset."
Cyclical oral progestogens are not contraceptive. If she is sexually active, pair them with contraception or choose the LNG-IUS.
"This tablet brings the prolactin down and usually shrinks the growth. Your periods — and fertility — often come back quickly, so think about contraception now if you don't want to get pregnant. Tell us if you notice urges you find hard to control."
In primary care the task is sequencing: sample taken properly, TSH, pregnancy, drugs and macroprolactin checked, visual fields examined, then imaging and referral. Cabergoline follows that sequence and is not a step in it.
"This helps your body use insulin better, which can help periods and weight. It can upset the stomach at first, so we start with a small dose with food. Because ovulation may return, use contraception if you don't want to get pregnant."
Metformin is an add-on to lifestyle, not a weight-loss drug in its own right. Screen for disordered eating before a weight-focused plan.
"Calcium and vitamin D are the building blocks, but oestrogen and enough fuel are the builders. On their own these won't fix your bones, but they make sure the materials are there."
A "calcium and vitamin D and a pill" plan for FHA is the classic incomplete answer. The examiner wants energy availability named as the treatment.
Sport & Athletic Identity
For Sophie, running is identity, stress relief and social life. Being told to "do less" feels like being told to be less. In sport culture, amenorrhoea is still sometimes seen as a sign of being fit and lean, and coaches or peers may reinforce under-fuelling.
Engaging a sports-medicine clinician or dietitian who works with athletes gives the advice credibility. The IOC REDs CAT2 frames modified participation as protective, not punitive.
"The aim isn't to take running away — it's to make sure you're strong enough to keep doing it for years. Lots of elite runners have been through exactly this."Food, Body Image & Control
Restriction can start as "clean eating for performance" and become rigid rules, anxiety around unplanned meals, and distress at rest days. Denial and minimisation are features of the illness, not dishonesty (site eating-disorder protocol).
If an eating disorder is suspected, refer promptly and hold the physical monitoring in primary care. A normal BMI does not exclude serious risk.
"Some people find food starts to feel like something they have to control. If that's ever true for you, it's not a failing — it's something we can get proper help with."Fertility — Spoken & Unspoken
Most patients will not raise fertility unless asked, yet it is often the hidden concern. In FHA and PCOS the outlook is usually good with treatment. In POI, the news that natural conception is unlikely is a bereavement and needs time, written information and specialist counselling, including the realistic role of donor eggs.
"Is having children something you think about for the future? I'd rather we talk about it now than leave you worrying."POI — Identity, Relationships & Menopause at 30
A menopause diagnosis in your twenties or thirties affects sexual function, relationships, self-image and mood. Low libido and vaginal dryness are rarely volunteered. Partners may need information too. Peer support from the Daisy Network, a UK POI charity, helps many women.
"This is a lot to take in, and it's not something most people your age have to deal with. How are you feeling about it — and is there someone at home who'd find it helpful to hear this too?"Work, Study & Stress
Work stress is a driver of FHA in its own right. Shift work, long hours and training fitted around a demanding job squeeze meals out. Clinic appointments for DXA, dietetics and review need to fit around work. A fit note is rarely needed, but advice on regular meal breaks can be.
"When does eating actually happen on a work day? Sometimes the fix is as practical as planning a snack before the evening run."Driving — When the Pituitary Is the Cause
Most causes of amenorrhoea have no driving implications. A pituitary tumour does if it affects the visual fields. Under DVLA guidance, a pituitary tumour with a visual field defect must be reported to the DVLA, and the patient must meet the visual field standard to drive. Some pituitary surgery also carries its own rules. A drug-treated prolactinoma with normal fields usually needs no notification. Check the current DVLA Assessing fitness to drive guidance. Severe anorexia nervosa with syncope or cognitive impairment may also make driving unsafe.
"Because the scan showed the growth is pressing near the nerves to your eyes, I need to talk about driving. Until your visual fields are checked properly, please don't drive, and we'll look at whether you need to tell the DVLA."1–2 Weeks — Results & Safety Check
Pregnancy test negative? Review FSH/LH, oestradiol, prolactin, TSH and testosterone. Act on any unexpected result: raised FSH (repeat, and consider POI), raised prolactin (repeat properly and follow the protocol sequence), raised testosterone (check the tempo). Check that the SCOFF was completed and the referrals were made. If weight is low or falling, carry out a MEED physical risk check: pulse, lying and standing BP, temperature, SUSS test, and U&E with phosphate and magnesium. Agree contraception.
~6 Weeks — Engagement & Trajectory
Has she seen the dietitian or sports medicine? Weight trend (clinic weight), training load, rest days, new bone pain, mood and stress. Is there any evidence of an eating disorder that was not apparent at first? If so, refer to the community eating disorders service now (NICE NG69). DXA booked or done?
~3 Months — DXA Result & Plan
Discuss the DXA result. In premenopausal women it is interpreted as a Z-score against age-matched controls, not a T-score. A low Z-score strengthens the case for specialist input. Is there any sign of recovery, such as cervical mucus, breast tenderness or a spontaneous bleed? Refresh the performance framing.
6–12 Months — Periods Back?
If yes: the energy balance is restored, so continue the plan and keep contraception in place. If no, despite a fair trial: first reconsider the diagnosis (repeat the hormone panel, and think about coeliac disease, a hidden eating disorder, or POI). Then refer to endocrinology or gynaecology to discuss short-term transdermal estradiol with cyclical progestogen (Endocrine Society 2017), particularly with low BMD or further bone injury.
Annual / Life Events — Bone, Fertility, Relapse
Repeat DXA only if the result would change management. In anorexia nervosa, do not repeat more often than once a year unless there is bone pain or recurrent fracture (NICE NG69). Pre-conception: if she wants to conceive and FHA persists, refer to fertility services. Increasing training for a new event is a relapse risk, so plan fuelling in advance. For other causes, see 7I: annual review in PCOS, HRT review in POI, and prolactin surveillance in prolactinoma.
Memory rule — amenorrhoea monitoring framework
At every review: pregnancy possible? (fertility can return before periods); bleeding diary (spontaneous vs withdrawal bleed); weight and physical risk (clinic weight; MEED observations if low or falling); bone (new pain, fractures, DXA plan); mind (mood, eating, stress); cause-specific safety (UKMEC for the COCP, B12/eGFR for metformin, valves and impulse control for cabergoline, endometrium in PCOS).
⚠ Three scenario-specific safety-net phrases
Why safety-netting matters beyond clinical care
- Prescribing the pill as the sole "treatment" for hypothalamic amenorrhoea
- Ignoring bone protection / eating-disorder screening
- Not counselling on fertility/contraception (fertility can return before periods)
Who you are
Sophie Carter, 26, training hard for a marathon. Your periods stopped about 8 months ago. You've cut your food intake to "stay lean" and lost weight (BMI now 18). Work is stressful. You're sexually active but use condoms and are sure you're not pregnant. No breast discharge, no excess hair/acne, no headaches/visual changes, no hot flushes. You're not trying for a baby and aren't bothered — you came because your mum nagged you. You had a stress fracture in your foot last year. You're slightly defensive if you think someone's going to tell you to stop running.
Hidden concerns (reveal if explored)
Fertility (deep down): if asked gently, you do wonder whether this could affect having children one day.
Fear of being told to stop training: running is central to your identity; you'll resist advice framed as "do less".
Eating: you're quite controlled around food; you may downplay it but will open up a little if asked kindly and without judgement.
Clinical details if asked
- Secondary amenorrhoea ~8 months; previously regular
- High training volume + restricted intake; weight loss; BMI 18; work stress
- No galactorrhoea, hirsutism/acne, headaches/visual symptoms, hot flushes/night sweats
- Sexually active, condoms; not trying to conceive; no relevant medications
- Previous foot stress fracture; no thyroid problems; no prior pregnancies/surgery
Reactions at key moments
- On the pregnancy test: "I told you I'm not pregnant" → accepts when told it's routine.
- On the bone/performance link: this lands — you didn't connect the stress fracture to your periods; becomes more engaged.
- On "not just the pill": relieved it's not just being handed medication.
- On eating questions: a little guarded; opens up if approached without judgement.
- Challenge line: "So are you telling me I have to stop running?"
Resolution: Sophie engages if the GP: (1) does a pregnancy test first despite her protests; (2) reasons along the HPO axis and sends the core panel, excluding PCOS/thyroid/prolactin/POI; (3) recognises functional hypothalamic amenorrhoea from low energy availability and connects the prior stress fracture to bone risk (female athlete triad); (4) screens eating sensitively and frames the plan around her performance and injury-prevention rather than "stop running"; (5) explains that restoring energy balance — not the pill — is the treatment, arranges dietetic/sports-medicine and bone (DXA) input, and counsels honestly on fertility (usually reversible; contraception still needed). She disengages if lectured, told bluntly to stop running, or simply handed the pill with no explanation.
Always pregnancy test first. Classify primary (no periods by 15/13) vs secondary (≥3–6 months). Core panel: FSH/LH, prolactin, TSH; oestradiol if hypogonadism suspected; testosterone + SHBG/FAI if hyperandrogenism/PCOS suspected. Localise: high FSH → POI; low/normal → hypothalamic/pituitary; high prolactin → pituitary (MRI if symptoms); high androgens → PCOS. Pelvic USS/karyotype/DXA as directed.
Hypothalamic: restore energy availability + dietetic/eating-disorder support + bone protection (not pill-only). PCOS: lifestyle, endometrial protection, metabolic/CV, fertility. POI: HRT to ~51 + fertility counselling + work-up. Hyperprolactinaemia: stop drug / dopamine agonist (specialist). Protect bone in all hypo-oestrogenic states; counsel fertility/contraception.