Dutasteride is an inhibitor of the 5-alpha reductase enzyme. Reductase inhibitors are designed to prevent the conversion of testosterone to its more androgenic counterpart DHT (dihydrotestosterone). DHT is implicated in a number of disorders in men including male pattern hair loss and benign prostate enlargement. Dutasteride is specifically approved for the treatment of symptomatic benign prostate hyperplasia (BPH). While dutasteride is similar in structure and action to finasteride, it differs from the first generation reductase inhibitor in its tissue selectivity. Finasteride inhibits the type-2 isozyme of the 5alpha reductase enzyme, found prominently in the scalp and prostate. Dutasteride is non-specific for isotype, and inhibits both type-1 and type-2 reductase. As such, it inhibits DHT conversion in all tissues including the scalp, liver, prostate, and skin. Because of this it also lowers systemic levels of DHT much more effectively than finasteride.