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Tour de France champion Floyd Landis tested positive for high levels of testosterone, but experts tell WebMD that there could be many reasons why.

Wire reports say that 30-year-old Landis tested positive for what is being called "an unusual level of testosterone:epitestosterone" during the three-week race.

"This is huge news," says steroid law expert and former body builder Rick Collins of Carle Place, N.Y.

But Collins is quick to add Landis is innocent until proven guilty.

"Don’t draw any conclusions yet and certainly if he didn't, in fact, consume testosterone, Landis should mount a very vigorous defense," says Collins, author of Legal Muscle.

For starters, the test looks at the ratio of testosterone to epitestosterone and is highly likely to yield false-positive results. The initial results must be confirmed by further testing and it is not yet known when this will occur. Until then, there is no conclusive evidence of doping, he says.

In the interim, Landis has been suspended. If Landis is found guilty of doping, he could be stripped of the Tour title and Spain's Oscar Pereiro would become champion, wire reports say.

"When balance between testosterone and epitestosterone are sufficiently far enough apart, it is deemed to be positive for doping," he says. But there are other reasons that this ratio can be off, he says. For example, studies have shown that a spike in testosterone can also result from certain circumstances occuring either before or after winning games, he says.

Testosterone Effects Not Immediate

At one point in the three-week race, it seemed as though Landis was petering out. But "an injection of testosterone is not some sort of miracle, immediate boost like an amphetamine or stimulant," Collins says. "Athletes who use testosterone use it over a fairly long course and the benefit accumulates over a period of time."

Testosterone would not account for his comeback, Collins stresses.

"A single shot of testosterone would provide little or no benefit."

John Eliot, PhD, a professor of human performance at Rice University in Houston, and the author of "Overachievement," agrees with Collins.

"The likelihood [that he used illegal substances] seems small to me," he tells WebMD. "Landis is a pretty straightforward guy and personality-wise he does not want to take the easy route," he says.

Could Hip Condition Be a Factor?

Landis is known to have a degenerative, painful hip condition.

"His body, in an attempt to recover, will naturally release more testosterone as part of the recovery process," Eliot says. Also "who knows what he is taking for the pain and this too could interfere with the testing results."

On the other hand, "if his hip was really falling apart, maybe the only way to finish the race was to take testosterone to block the pain," he suggests.

Exactly when he tested positive is also somewhat suspicious, says Eliot. The test was done at stage 17, which coincides with one of the most intense parts of the race.

"The more heavily we exert ourselves, the more naturally our body releases testosterone," he says.

"Fans assume guilt until innocence is proven, but there are a lot of reasons to believe he could be innocent," he says.

Carlos R. Hamilton Jr., MD, professor of medicine and an endocrinologist at University of Texas Health Sciences Center in Houston, and a member of the health, medical, and research committee of the World Anti-Doping Agency, is also reserving his judgment.

"The fact that it is strictly a testosterone level does not mean it came from outside of the body, it could have been produced internally," he says. "It's a perfectly normal occurring hormone."

He says that there is a large variation in what they consider normal on this test and no one knows exactly how Landis scored. "Were his results within normal limits or just out of sight?" he asks.

The bottom line is that the information was released too prematurely, he says. "Wait until we get the final answers. If he cheated, it will be recognized; if he did not, this does him a great disservice."

By Denise Mann, reviewed by Louise Chang, MD

SOURCES: Rick Collins, steroid law expert and former body builder, Carle Place, N.Y. John Eliot, PhD, professor, human performance, Rice University, Houston; and author, Overachievement. Carlos R. Hamilton, JR, MD, professor of medicine and endocrinologist oat University of Texas Health Sciences Center in Houston; and a member, health medical and research committee, World Anti-Doping agency.