Finasteride is the first selective type2 5α-reductase inhibitor, which blocks the conversion of testosterone to 5α-dihydrotestosterone (DHT) in target organs such as the prostate and scalp hair. It also has been studied for its ability to reduce the incidence of prostate cancer.
Finasteride: an update of its use in the management of symptomatic benign prostatic hyperplasia. 
Finasteride: a review of its use in male pattern hair loss. 
A new look at the 5alpha-reductase inhibitor finasteride. 
The Rationale for Inhibiting 5α-Reductase Isoenzymes in the Prevention and Treatment of Prostate Cancer. 
Type 1 and type 2 5alpha-reductase expression in the development and progression of prostate cancer.