The 55 men in a drug doping study in Sweden were normal and healthy. And all agreed, for the sake of science, to be injected with testosterone and then undergo the standard urine test to screen for doping with the hormone.
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 gene deletion is especially common in Asian men, notes Jenny Jakobsson Schulze, a molecular geneticist at the Karolinska University Hospital in Stockholm. Dr. Schulze is the first author of the testosterone study, published recently in The Journal of Clinical Endocrinology and Metabolism.
The whole “Asian” angle wouldn’t be as important from where I stand if China wasn’t intent on becoming an athletic superpower. Specifically, from Doping Test Results Dependent on Genotype of UGT2B17, the Major Enzyme for Testosterone Glucuronidation:
We demonstrated that a deletion polymorphism in the gene coding for UGT2B17…is strongly associated with TG levels in urine…All subjects devoid of the gene had a T/E ratio below 0.4…This polymorphism was considerably more common in a Korean Asian than in a Swedish Caucasian population, with 66.7 and 9.3 % deletion/deletion (del/del) homozygotes respectively.
They don’t seem to know what SNP is causing this. If you are curious, you can check out the linkage disequilibrium around UGT2B17.