[Hirsutism: a common problem; when to consider rare causes?]

Excessive hair growth is a common and distressing complaint in women. It is imperative to differentiate excessive hair growth from hirsutism with possible other signs of virilization. Hirsutism is commonly attributed to polycystic ovary syndrome (PCOS). Hirsutism with rapid onset or progression, potentially combined with other signs of virilisation or secondary amenorrhea, should prompt evaluation of other underlying causes. In this clinical lesson, we present three cases of hirsutism to illustrate red flags to consider rare diagnoses. Diagnoses include non-classical congenital adrenal hyperplasia, a testosterone-secreting Leydig-cell tumour and PCOS. Early recognition and diagnosis can improve quality of life and, in cases of malignancy, enhance survival outcomes.