Arimidex, also known as Anastrozole, is a selective aromatase inhibitor commonly used in bodybuilding and hormone replacement therapy (HRT) to reduce estrogen levels. It works by blocking the enzyme aromatase, which is responsible for converting testosterone into estrogen. This makes it especially useful for preventing estrogen-related side effects such as water retention, gynecomastia, and fat gain. Ideal for athletes and bodybuilders looking to control estrogen levels during steroid cycles or HRT.