Cyproterone acetate

What it is

Cyproterone acetate is a progestin that also blocks the androgen receptor and lowers gonadotropins. In Europe it is sold alone (higher dose) and in low-dose combinations with ethinyl estradiol. It is prescription-only. In 2020 the EMA's safety committee restricted products containing 10 mg or more to androgen-dependent conditions (hirsutism, androgenic alopecia, acne, seborrhoea), only after other options, including lower doses, have failed. EMA PRAC 2020 We did not verify US availability.

What the studies show

• Versus minoxidil (66 women, 12 months, randomised): cyproterone acetate 52 mg with ethinyl estradiol 35 mcg lost hairs over 40 micrometres (-2.4 per 0.36 cm²), while the minoxidil 2% group gained (+6.5). Cyproterone did relatively better when other signs of excess androgen were present, and it improved oily skin more. Vexiau 2002
• Four-drug comparison (48 women, 1 year, unmasked): the cyproterone arm was not statistically significant; only flutamide improved. Carmina 2003
• Open series (80 women, 12 months or more): 44% regrew and 44% were stable on spironolactone or cyproterone, with similar results and no placebo. Sinclair 2005
• The two randomised trials disagree: one found net hair loss against minoxidil, the other was small and unmasked. The Cochrane review of women's hair loss treatments is useful context. van Zuuren 2016

Side effects and safety

• Meningioma (usually a benign brain tumour): in a French cohort of 253,777 women starting high-dose cyproterone, the adjusted hazard ratio for meningioma surgery or radiotherapy was 6.6 (95% CI 4.0 to 11.1), rising to 21.7 above 60 g cumulative dose. Weill 2021 The EMA found no evidence of this risk for low-dose combinations with ethinyl estradiol or estradiol valerate but advises against them if there is a meningioma history. EMA PRAC 2020
• Pregnancy: must be avoided on antiandrogens because of the risk of feminising a male fetus; the same class warning applies to bicalutamide and spironolactone.

Bottom line

For women, a clinician may choose cyproterone where acne, excess hair or irregular periods coexist with thinning, at the lowest effective dose for the shortest time. Evidence is limited and mixed, and most specialists now start with spironolactone or minoxidil. It is not for men with hair loss, and the meningioma risk at high doses is serious. Discuss with a doctor.