Influence of Estrogens on Androgen Metabolism in Different Subunits of Human Hair Follicles

The study investigated the effects of estrogens on androgen metabolism in human hair follicles, particularly focusing on the enzyme 5alpha-reductase (5alpha-R) which is involved in the conversion of testosterone to dihydrotestosterone (DHT), a key factor in androgenetic alopecia. Scalp biopsies from volunteers were used to examine the impact of 17alpha-estradiol (E) and 17beta-E on 5alpha-R, 3beta-hydroxysteroid dehydrogenase (3beta-HSD), and 17beta-hydroxysteroid dehydrogenase (17beta-HSD) activities. The study found that finasteride was a potent inhibitor of DHT formation, reducing its synthesis by 86% at 1 nM concentration, while progesterone inhibited it by 75%. In contrast, estrogens were less effective, with 100 nM 17alpha-E and 17beta-E reducing DHT synthesis by 20% and 60%, respectively. The study suggested that estrogens might inhibit DHT formation indirectly by promoting the conversion of testosterone to weaker androgens, but further research was needed to confirm this mechanism.