Finasteride

Testosterone, the principal circulating androgen, acts directly in many tissues. To be active in the prostate and skin, testosterone must be converted to dihydrotestosterone by the enzyme 5α-reductase (Figure 1). Most dihydrotestosterone in the prostate arises from testicular precursors, although some arises from adrenal precursors1. In women, although the relative ovarian and adrenal contributions to intracellular dihydrotestosterone are unknown, the two organs contribute equally to testosterone production2. Finasteride is one of several inhibitors of 5α-reductase that have recently been developed. These drugs selectively block dihydrotestosterone production and androgen action in the prostate and skin. Finasteride (Proscar) has been . . .