Polycystic Ovary Syndrome (PCOS)

🔍 When to Suspect

A combination of oligo/anovulation (irregular periods), clinical/biochemical hyperandrogenism (hirsutism, acne), and/or polycystic ovaries on ultrasound

From the full topic in The Ocean Library: Polycystic Ovary Syndrome (PCOS)

🧭 When to suspect

Suspect polycystic ovary syndrome (PCOS) in a woman of reproductive age with oligo- or anovulation (usually irregular or absent periods), clinical or biochemical hyperandrogenism (hirsutism, acne, or female-pattern hair loss), or polycystic ovarian morphology (PCOM) on ultrasound. It is common – affecting around 1 in 8 women – and usually presents in adolescence or early adulthood.

The condition has recently been renamed: by international consensus (announced at the European Congress of Endocrinology in May 2026), PCOS is now termed polyendocrine metabolic ovarian syndrome (PMOS), reflecting its multisystem endocrine and metabolic nature rather than a disorder of ovarian cysts. NICE's first UK guideline – an adaptation of the 2023 international guideline – is in draft for public consultation, with the final version expected December 2026. Because PCOS remains the term in current UK clinical systems, coding and patient materials, this article uses PCOS throughout while noting PMOS as the incoming name.

The two core primary-care tasks are to make a positive diagnosis safely – without missing the rare androgen-secreting tumour – and to manage the condition as a lifelong cardiometabolic disorder rather than merely a menstrual or cosmetic one. Diagnosis follows the exclusion of mimics and rests on two of the three features below.

Diagnostic feature	Description
Ovulatory dysfunction	• Infrequent or absent ovulation – usually manifest as infrequent or no menstruation.
Clinical or biochemical hyperandrogenism	• Hirsutism, acne, or raised total/free testosterone. • Hirsutism alone predicts biochemical hyperandrogenism and PCOS; acne or female-pattern hair loss in isolation are weaker predictors.
Polycystic ovarian morphology (PCOM)	• ≥ 20 follicles in at least one ovary on ultrasound. • Polycystic ovaries are neither necessary nor sufficient for the diagnosis on their own.

In adults, diagnose when any two of three are present; the condition may be more prevalent, and criteria may differ, in women of Black, Asian or mixed ethnicity. In adolescents (within 8 years of menarche), both hyperandrogenism and irregular cycles are required – take great caution where androgen excess occurs without menstrual irregularity. Those with features who fall short are at "increased risk" and should be reassessed by 8 years post-menarche, particularly if features predate the combined pill, persist, or accompany significant adolescent weight gain.

A diagnosis is regarded as enduring: it can be made postmenopausally from a past diagnosis or a reproductive-years history of oligo-/amenorrhoea with hyperandrogenism, but new, severe or worsening postmenopausal hyperandrogenism warrants investigation for an androgen-secreting tumour or ovarian hyperthecosis.

Source: International PCOS Guideline 2023 · RCOG · NICE draft guideline 2026

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