The race between two US baseball players to achieve a record number of home runs in one season has focused US national attention on the increasing use of performance enhancing dietary supplements by athletes.

Baseball players Mark Mc-Gwire and Sammy Sosa have admitted consuming creatine, an energy boosting protein. Mark McGwire also admits to taking androstenedione, a testosterone precursor. Both substances are readily available over the counter, and because they are labelled as dietary supplements they are not subject to regulation by the Food and Drug Administration.

The enthusiastic endorsement of such substances by high profile professional athletes has raised their popularity among teenagers, college athletes, and amateur athletes. It has also led to more inquiries into the safety of such supplements.

Androstenedione, a …