Synopsis
Assess absent or infrequent menstruation systematically, exclude pregnancy and urgent pathology, localise reproductive-axis dysfunction, and protect fertility, bone and endometrial health.
- Oligomenorrhoea means persistently infrequent cycles; secondary amenorrhoea generally merits assessment after three months without bleeding when cycles were regular, or six months when they were previously irregular.
- Primary amenorrhoea requires evaluation by age 15 or more than three years after breast development begins; absent secondary sexual development at 13 is an earlier referral trigger.
- Exclude pregnancy before interpreting reproductive hormones, even when contraception is reported, fertility seems unlikely or occasional spotting has occurred.
- Use history and examination to separate ovarian androgen excess, ovarian insufficiency, hypothalamic energy or stress suppression, hyperprolactinaemia, thyroid disease, uterine or outflow pathology and medicine effects.
- FSH with oestradiol helps localise the axis: raised FSH with low oestradiol suggests ovarian insufficiency, while low or inappropriately normal gonadotrophins with low oestradiol suggests central suppression.
- Pelvic ultrasound defines uterine anatomy, endometrial appearance and ovarian morphology but neither confirms PCOS by itself nor excludes endocrine disease.
- Management is cause directed and goal specific: contraception, desired fertility, endometrial protection, oestrogen replacement and recovery of adequate energy availability are different clinical aims.
- Amenorrhoea is not reliable contraception; ovulation can resume unpredictably during recovery from hypothalamic suppression, prolactin treatment or intermittent ovarian function.
Key red flags
A positive pregnancy test with unilateral pelvic pain, shoulder-tip pain, bleeding, collapse or peritoneal signs needs urgent assessment for ectopic pregnancy.
New severe headache, vomiting, visual-field change, ophthalmoplegia, polyuria or polydipsia raises concern for pituitary or hypothalamic disease and requires expedited endocrine imaging assessment.
Rapidly progressive hirsutism, voice deepening, clitoromegaly or a new abdominal mass suggests an androgen-secreting ovarian or adrenal disorder rather than uncomplicated PCOS.
Bradycardia, hypotension, orthostasis, hypothermia, electrolyte abnormality, recurrent syncope or very low weight in a person with restricted intake or excessive exercise warrants urgent medical and eating-disorder assessment.
Primary amenorrhoea with cyclical severe pelvic pain or a palpable mass may reflect obstructed menstrual outflow and requires prompt gynaecological examination and imaging.
Investigation priorities
Exclude pregnancy before endocrine classification or hormonal treatment.
Management branches
A person presents with absent or persistently infrequent menstruation.
- Clarify primary versus secondary amenorrhoea, cycle timing, pregnancy possibility, contraception, pain, bleeding, pubertal development and the person's reproductive goal.
- Check hCG, observations and red flags before arranging routine endocrine testing; escalate pregnancy symptoms, neurological change, virilisation or nutritional instability immediately.
- Review weight trajectory, intake, exercise, stress, chronic disease, uterine procedures and every relevant medicine, then perform a consented targeted examination.