The human body produces many forms of steroids naturally. Anabolic steroids are drugs that resemble the chemical structure of the body's natural sex hormone testosterone. Androstenedione is a steroid hormone that can be broken down into testosterone. Testosterone is naturally made by the bodies of males and, in much smaller amounts, females. The hormone directs the body to produce or add male characteristics such as increased muscle mass, facial hair, and deep voices, and is an important part of male development during puberty.

When athletes take anabolic steroids, these drugs stimulate the muscle tissue in their bodies to grow larger and stronger, exaggerating the effects of testosterone on the body. The effects of too much testosterone ciculating in the body is harmful over time.

Updated and reviewed by: Kim Rutherford, MD
Date reviewed: February 2002
Originally reviewed by: Steven Dowshen, MD