The muscle-building supplement that Mark McGwire made famous, Androstenedione (Andro), is classified as a steroid and as such, it is illegal to use without a legitimate medical reason. For years Major League Baseball did not ban andro despite evidence that its use could be hazardous to those taking it without a legitimate medical reason. It had been previously been banned by the Anti-Doping Agency, International Olympic Committee, the NCAA, the NFL and the men's and women's tennis tours.
In January of 2005, the Anabolic Steroid Control Act was amended with the Controlled Substance Act that added anabolic steroids and prohormones to the list of controlled substances. This makes possession of the substances a federal crime. In 2004, the United States Food and Drug Administration (FDA) banned the sale of Andro, because of evidence to support increased health risk when using this substance.
Androstenedione is a supplement made from a naturally occurring steroid hormone. The body metabolizes androstenedione into testosterone, which is considered a steroid. When supplements of testosterone are taken in high doses, they are known to have an anabolic effect increasing muscle size and strength.