Androstenedione

Androstenedione is a 19-carbon steroid hormone produced in the adrenal glands and the ovaries as an intermediate step in the biochemical pathway that produces the androgen testosterone and the estrogens estrone and estradiol. Some androstenedione is also secreted into the plasma, and may be converted in peripheral tissues to testosterone.

The production of adrenal androstenedione is governed by ACTH, not by gonadotropins.

Androstenedione is manufactured as a dietary supplement, often called andro for short. The substance has similar effects to anabolic steroids when taken as a supplement, allowing users to build muscle mass. Andro was in common use in Major League Baseball throughout the 1990s by record breaking sluggers like Mark McGwire. The supplement is banned in the Olympics.

On March 11, 2004, the United States Food and Drug Administration sent warning letters to 25 manufacturers warning them to stop selling andro supplements. The FDA's position is that andro supplements pose significant health risks.