5 α -Reductase Inhibitors in the Treatment of Androgenetic Alopecia

In men with androgenetic alopecia (AGA; male pattern hair loss), endogenous androgens cause progressive miniaturization of scalp hair follicles, leading to a steady decline in visible scalp hair density and, eventually, baldness. Dihydrotestosterone (DHT), a metabolite of testosterone produced by the enzyme 5α-reductase, has been identified as the specific androgen involved in the pathogenesis of AGA, thus providing a rationale for the use of 5α-reductase inhibitors in the treatment of men with AGA. Finasteride is a specific and potent inhibitor of human type 2 5α-reductase. Originally developed for the treatment of men with benign prostatic hyperplasia, finasteride was subsequently evaluated as a treatment for patients with AGA. Clinical studies in balding men demonstrated that treatment with finasteride reduced scalp DHT levels and led to improvement in scalp hair growth, confirming both the role of DHT in the pathophysiology of AGA in men and the utility of inhibiting DHT production in the treatment of the disorder. In contrast to its beneficial effects in men, finasteride was not effective in the treatment of AGA in postmenopausal women, suggesting that AGA may have a different pathophysiology in women compared to men. The success achieved with finasteride in the treatment of men with AGA has stimulated the study of other 5α-reductase inhibitors in the treatment of this disorder. This review examines the recent advances in the development of 5α-reductase inhibitors in the treatment of men with AGA.