Synopsis
Apply adult and adolescent PCOS criteria correctly, document hyperandrogenism and ovulatory dysfunction, and exclude pregnancy, endocrine mimics and dangerous androgen excess.
- In adults, diagnose PCOS after excluding relevant alternatives when at least two of three features are present: ovulatory dysfunction, clinical or biochemical hyperandrogenism, and polycystic ovarian morphology on ultrasound or an accepted adult AMH alternative.
- When irregular cycles and hyperandrogenism are both established, ovarian ultrasound or AMH is unnecessary for diagnosis and can create confusion rather than certainty.
- Do not use AMH as a standalone test, combine AMH and ultrasound to inflate the morphology criterion, or apply either test for diagnosis during adolescence.
- Adolescents require both persistent ovulatory dysfunction defined by years since menarche and clinical or biochemical hyperandrogenism after mimics are excluded; review those with partial features over time.
- Prefer calculated free testosterone or free androgen index with a reliable total testosterone assay; combined oral contraception makes biochemical interpretation difficult and may need a supervised three-month washout if testing is essential.
- Exclude pregnancy, thyroid disease, hyperprolactinaemia and non-classic congenital adrenal hyperplasia in the appropriate presentation; investigate Cushing syndrome or androgen-secreting disease when their clinical signals are present.
- Polycystic ovaries are follicles, not pathological cysts requiring drainage or removal, and morphology alone is common in people without the syndrome.
- The NHS now uses the public-facing term polyendocrine metabolic ovarian syndrome, but current professional guidance and this curriculum retain PCOS; explain the terminology without changing the diagnostic construct.
Key red flags
Voice deepening, clitoromegaly, rapidly increasing muscle mass or fast progression of terminal hair suggests severe androgen excess rather than the usual gradual PCOS phenotype.
A very high or rapidly rising testosterone or DHEAS concentration requires confirmation with a high-quality assay and urgent investigation for ovarian or adrenal pathology.
Headache, visual change or galactorrhoea directs assessment toward pituitary disease and hyperprolactinaemia rather than assuming PCOS explains irregular cycles.
Cushingoid bruising, broad violaceous striae, proximal weakness or facial plethora warrants targeted cortisol assessment where clinical suspicion is genuine.
A positive pregnancy test, pelvic pain or abnormal bleeding must enter the pregnancy pathway before diagnostic hormone interpretation.
Investigation priorities
Exclude common consequential alternatives to PCOS in a person with irregular or absent cycles.
Management branches
An adult presents with irregular cycles, androgenic symptoms or a prior report of polycystic ovaries.
- Define cycle pattern and assess clinical hyperandrogenism, pregnancy possibility, hormonal treatment, symptom tempo and red flags for severe endocrine disease.
- Confirm biochemical androgens when needed and exclude thyroid, prolactin, adrenal and other alternatives in proportion to the clinical presentation.
- Use ultrasound or AMH only if the morphology domain is needed, then record exactly which two of three domains establish the diagnosis.