Aromasin (Exemestane) belongs to the group of aromatase inhibitors. It has even more powerful aromatase inhibiting ability than Anastrozole. Unlike Anastrozole and Letrozole, Exemestane inactivates aromatase completely and irreversibly. Exemestane reduces the production of estrogen in the body. The drug was approved in the United States for the treatment of breast cancer. In bodybuilding, Aromasin is used as a part of steroid treatment to reduce conversion of testosterone to estrogen when taking anabolic hormones.