A genetic variant common among East Asians masks the use of performance-enhancing testosterone prohibited in top-level sports competition, a new study showed.
Athletes with a slightly different expression of the same gene, by contrast, run the risk of being falsely accused of doping, the study said.
The standard test in professional and amateur sports for uncovering illicit testosterone use measures the ratio of two chemicals in the urine.
The level of testosterone glucuronide (TG), a by-product of testosterone in the body, is compared with the level of epitestosterone glucuronide (EG), which remains constant even when the power-boosting hormone is injected into the blood stream.
Any ratio above four to one is seen as suspect, according to the International Olympic Committee.
But depending on how many copies one has of a gene known as UGT2B17, the results of the test can vary 20-fold, allowing drug cheaters to go undetected or yielding “false positives” for clean athletes.
A team of researchers led by Jenny Jakobsson at the Karolinska Institute in Stockholm injected 55 male volunteers with 500mg of testosterone enanthate, a substance banned by virtually all sports federations.
The subjects were divided into three groups, depending on whether they had one, two or no copies of UGT2B17.
More than 40 percent of the men who had no copies of the gene showed testosterone levels within permissible bounds in daily urine tests over the next 15 days despite having taken a large dose of a banned substance.
By contrast, 100 percent of the other two groups tested positive, said the study, which was published in the Journal of Clinical Endocrinology and Metabolism.
“Nearly half of the individuals in our study who carried this genetic variation would go undetected in a regular doping test,” Schulze said.
Previous research has shown that the genetic variant that can mask hormone use is more common among East Asians than Caucasians by a ratio of seven to one, according to Jakobsson.
She said that if doping controls for testosterone are to be effective, they need to take genes into account.
“Genotyping as a complement to the conventional urine analysis would improve the sensitivity of the test” by adjusting benchmarks according to one’s genetic endowment, she said.
Synthetic steroids and testosterone build up muscle tissue, and have been by far the most frequently detected illicit substance used in sports, accounting for 43 percent of positive results in 2005, according to the World Anti-Doping Agency.
■ STRIKE HINDERS TESTING
DPA, STOCKHOLM
A strike among Swedish nurses and other members of the Swedish Association of Health Professionals has begun to impact on the doping test program for top Swedish athletes, reports said yesterday.
Mats Garle, head of the main Swedish doping laboratory at Huddinge hospital, was quoted as telling the newspaper Dagens Medicin that blood samples risked being destroyed since no staff were able to handle them.
“All samples are just kept here pending the strike to end,” Garle told the newspaper.
The strike involving 3,500 nurses countrywide began on Monday after a government-appointed mediator gave up efforts to broker a wage deal.
The lab at Huddinge hospital receives some 100 samples a week from the national sports federation, and four Huddinge lab technicians were on strike.
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