Finasteride (marketed as Proscar, Propecia, Fincar, Finpecia, Finax, Finast, Finara, Finalo, Prosteride, Gefina, Finasterid IVAX) is an antiandrogen which acts by inhibiting type II 5-alpha reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT). It is used as a treatment in benign prostatic hyperplasia (BPH) in low doses, and prostate cancer in higher doses. It is also indicated for use in combination with doxazosin therapy to reduce the risk for symptomatic progression of BPH. Additionally, it is registered in many countries for androgenetic alopecia (male-pattern baldness). Finasteride was approved initially in 1992 as Proscar, a treatment for prostate enlargement, but the sponsor had studied 1 mg of finasteride and demonstrated hair growth in male pattern hair loss. On December 22, 1997, the FDA approved finasteride to treat male pattern hair loss. The Prostate Cancer Prevention Trial (PCPT) showed at a dosage of 5mg per day, as is commonly prescribed for BPH, though much higher than the 1mg generally prescribed for hair loss, participants taking finasteride were 25% less likely to have developed prostate cancer at the end of the trial compared to those taking a placebo. Further, finasteride increased the specificity and selectivity of prostate cancer detection, thus, a seemly increased rate of high Gleason grade tumor. Recognized side effects, experienced by around >1% of users, include erectile dysfunction, and less often gynecomastia (breast gland enlargement). As expected from its short 6-8 hour half-life, in trial studies, side effects ceased after dosage was discontinued.