Prostate Cancer Chemoprevention

5α-reductase is a nuclear membrane-bound NADPH-dependent δ-3-ketosteroid 5α-oxidoreductase. It is found in androgen-sensitive tissues, and catalyzes the conversion of testosterone to dihydrotestosterone (DHT). Two known isoenzymes of 5α-reductase have been identified: Type 1 predominates in peripheral tissues such as the skin and liver, and Type 2 is predominant in the prostate. Finasteride is a specific inhibitor of the Type 2 isoenzyme, and effectively blocks the Type 2-mediated conversion of testosterone to DHT, but does not inhibit the binding of DHT to the androgen receptor (AR) (1).