🧭 When to suspect

Hirsutism is excessive growth of thick, dark, terminal hair in a female in a male (androgen-dependent) pattern – typically the upper lip, chin, jawline, chest, abdomen, lower back and inner thighs. It reflects either an excess of circulating androgens or increased skin sensitivity to normal androgen levels, and is common, affecting up to 10% of women of reproductive age.

Distinguish it from hypertrichosis – generalised, androgen-independent excess hair (including fine vellus hair) that is not in a male pattern and is usually drug-induced or constitutional. Only true hirsutism warrants an androgen work-up.

The two clinical priorities in primary care are to identify the (usually benign) cause – polycystic ovary syndrome (PCOS) accounts for around 70–80% of cases and idiopathic hirsutism for most of the rest – and to recognise the rare sinister presentation: rapid onset, virilisation, or a markedly raised testosterone pointing to an androgen-secreting tumour.

Likely cause	Pointers
PCOS (most common)	Gradual onset from puberty, oligo/amenorrhoea, acne, raised BMI, family history; testosterone normal or mildly raised (typically < 5 nmol/L).
Idiopathic hirsutism	Regular cycles, normal androgens, no other features; a diagnosis of exclusion.
Non-classic congenital adrenal hyperplasia (CAH)	Onset around puberty, family history, higher-risk ethnic background; raised 17-hydroxyprogesterone.
Androgen-secreting tumour (ovarian/adrenal)	Rapid onset and progression, virilisation, markedly raised testosterone (usually > 5 nmol/L).
Cushing's syndrome	Central obesity, violaceous striae, proximal muscle weakness, easy bruising, hypertension.
Drug-induced	Anabolic steroids, danazol, sodium valproate, ciclosporin; androgens usually normal.

Raise the threshold for concern in any woman with rapidly progressing hair growth, signs of virilisation, or a postmenopausal first presentation, as these carry a higher likelihood of underlying neoplastic or adrenal disease.

Source: Society for Endocrinology · Endocrine Society

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