How Athletes Can Exploit the Testosterone Loophole Explained in New Study

The New York Times highlights the “testosterone loophole” in anti-doping tests reporting on a recent study that finally explains the phenomena that allows some athletes to get away with indiscriminate use of exogenous testosterone. This is the same study that has been discussed in the blogosphere for over a month on various doping and steroid-related websites including MESO-Rx, Steroid Report, Trust But Verify and Rant Your Head Off. But the New York Times story will provide mainstream exposure to the weakness in current doping protocols implemented by WADA using the testosterone:epitestosterone (T:E) ratio test (“Some Athletes’ Genes Help Outwit Doping Test,” April 30).

Researchers have long known that some men, Asians in particular, seemed to be able to take the drugs without getting caught, although no one had identified the cause of the phenomenon. Without gene testing, there is no way to know whether any athletes have exploited this doping loophole, but Dr. Catlin says he suspects some athletes discovered their invulnerability by accident and took advantage of it.

Men with the gene deletion still metabolize testosterone, Dr. Schulze says. But, she adds, she does not know where the hormone goes. We have no idea, she said. That’s what we’re trying to find out.

The gene in question adds a chemical, glucuronide, to testosterone. That converts it from a substance that dissolves in oil into one that dissolves in water and urine.

Athletes with a specific gene deletion (UGT2B17 homozygous deletion/deletion genotype) are genetically predisposed to pass the testosterone doping test.

The results were unambiguous: the test worked for most of the men, showing that they had taken the drug. But 17 of the men tested negative. Their urine seemed fine, with no excess testosterone even though the men clearly had taken the drug.

It was, researchers say, a striking demonstration of a genetic discovery. Those 17 men can build muscles with testosterone, they respond normally to the hormone, but they are missing both copies of a gene used to convert the testosterone into a form that dissolves in urine. The result is that they may be able to take testosterone with impunity.

The New York Times also reports that the “prevalence in other groups is not known.” But this is inaccurate. As reported in MESO-Rx last month, there is a lot of data on other groups involving the UGT2B17 gene.

(Thanks to Rehan Jalali of TSRF for alerting me to the Times article.)

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