The effect of spironolactone on genital skin 5α-reductase activity

In 1985, a study evaluated the effect of spironolactone on genital skin 5 alpha-reductase activity, which is involved in the conversion of testosterone to dihydrotestosterone (DHT), in hirsute women (HW) and in vitro. Thirteen hirsute women with a Ferriman-Gallwey score of 23.3 ± 2.8 were treated with 100 mg of spironolactone twice daily for a month, while 23 non-hirsute women served as controls. The study found that hirsute women had significantly higher conversion ratios of testosterone to DHT compared to controls. After treatment, these conversion ratios and the mass of DHT produced significantly decreased. In vitro, spironolactone also inhibited the conversion of testosterone to DHT, with the maximum effect at a concentration of 1.2 X 10^(-5) M. The study concluded that spironolactone directly inhibits 5 alpha-reductase activity, which may partly explain its beneficial effect in treating hirsute women.