Avodart inhibits a hormone known as DHT (dihydrotestosterone). DHT is a hormone that appears to cause hair loss (also known as MPB - Male Pattern Baldness) in most men. DHT is also the main cause of prostate enlargement in many men (also known as BPH - Benign Prostatic Hyperplasia).

Avodart works by inhibiting the activities of two types of 5-alpha-reductase enzymes. These enzymes are responsible in the body for converting testosterone to dihydrotestosterone (DHT). Avodart will lower DHT levels substantially.