Landis' team revealed Thursday that his urine sample last week showed "an unusual level of testosterone/epitestosterone."
Testosterone creams, pills and injections can build muscle and strength and improve recovery time after exertion when used over a period of several weeks, according to Dr. Gary Wadler, a member of the World Anti-Doping Agency and a spokesman for the American College of Sports Medicine.
But if Landis had been a user, earlier urine tests during the Tour would have been affected, too, Wadler said. Landis' first reported abnormal result was last Thursday, after his amazing come-from-behind performance in stage 17 of the race.
One-time use of steroids could result in an abnormal test, but it would have no effect on performance and could not account for Landis' astounding feat Thursday, "so something's missing here," Wadler said. "It just doesn't add up."
The test detects both testosterone and a related steroid called epitestosterone, which is not performance-enhancing. Both are produced by the body and are also made in synthetic form.
Suspicions for improper steroid use arise when the ratio climbs above 4 parts testosterone over 1 part epitestosterone, Wadler said. Officials have not said what ratio Landis' test showed.
Athletes who use performance-enhancing anabolic steroids often also take synthetic epitestosterone to equalize the ratio, said Charles Yesalis, a recently retired Pennsylvania State University professor and doping expert.
There is no medical use for synthetic epitestosterone; it is used "to cheat drug tests," Yesalis said.
Some men have naturally occurring high levels of testosterone and/or epitestosterone, but there is a sophisticated lab test called a carbon isotope ratio test that is often used to detect synthetic forms.
Alcohol can influence testosterone-epitestosterone levels, but more often in women than in men and it would be unlikely to have a huge effect, Wadler said.
Landis said in an interview during the Tour de France that he has had injections of cortisone, a medically used steroid drug to treat pain from a degenerating arthritic hip, but doctors said that would not affect his test results.
Corticosteroids "have zero impact" on the testosterone-epitestosterone test, Wadler said.
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