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Testosterone, epitestosterone and the doping tests

The situation of Tour winner Floyd Landis has focused attention on testing for testosterone.

The situation of Tour winner Floyd Landis has focused attention on testing for testosterone. (Image credit: Sirotti)

The standards of testing necessary to find an athlete guilty of doping with testosterone are among the most complex in anti-doping science because testosterone is a naturally-occurring hormone. Cyclingnews fitness panelist Dr Pam Hinton, assistant professor of Nutritional Sciences at the University of Missouri-Columbia, looks at the science of detecting testosterone use.

Many fans of cycling want to know that an elevated ratio of testosterone (T) to epitestosterone (E) is not synonymous with testosterone doping. It is not. In fact, the World Anti-Doping Agency's Guideline for Reporting and Management of Elevated T/E Ratios states, "An elevated T/E may be an indicator of the use of a prohibited substance." Before declaring an athlete positive for testosterone doping, additional testing is required. As with GH and EPO, doping with testosterone is difficult to detect.

This is because the form of the hormone that is available for exogenous administration is chemically identical to what is produced naturally in the body. Only a small fraction (about one percent) of the testosterone produced every day is excreted in the urine. Blood and urine levels increase after taking testosterone. But because the half-life of testosterone is very short, about one hour, blood and urine levels return to normal very quickly. Thus, measuring testosterone levels in urine is not an effective means of detecting steroid abuse.

There are two alternate methods currently in place to detect testosterone misuse. The first is to examine the ratio of testosterone to epitestosterone. Epitestosterone also is produced naturally in the body; it is chemically identical to testosterone with the exception of the hydroxyl group on C-17. A study of nearly 4000 male athletes reported the median T/E ratio to 1/1 with 99 percent of the men having a ratio less than 5.6/1. Another sample of about 5000 male athletes found the mean ratio to be 1.5/1.

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