LONDON (Reuters) - As Olympic officials prepare a bigger dope testing program than at any previous Games, researchers say a common genetic variation may be helping some athletes to beat testosterone doping tests and get away with cheating.
People with this change had normal testosterone levels even after they were injected with high levels of the steroid, said Jenny Schulze, a geneticist at Sweden’s Karolinska Institute, who worked on the study.
“Genetic factors may play an important role in the accuracy and sensitivity of testosterone doping tests,” Schulze said. “This is of interest not only for combating steroid doping in sports, but also for detecting and preventing steroids abuse in society.”
Athletes have long used testosterone to gain a competitive edge. The male hormone -- one of the most commonly used anabolic steroids -- increases muscle size and strength as well as helping to speed recovery from training or injury.
The World Anti-Doping Agency (WADA), which funded the Swedish research, has sought to stamp out steroids amid a slew of recent drug-related scandals in a range of sports.
U.S. cyclist Floyd Landis received a two-year ban after a French laboratory turned up traces of synthetic testosterone in a sample he provided during the 2006 Tour de France.
Prosecutors in the United States plan to seek a new criminal indictment of Major League Baseball’s all-time home run leader Barry Bonds stemming from an investigation into drug use in sports.
Olympic 100 meters champion Justin Gatlin is appealing against a four-year doping ban for testing positive for testosterone in 2006.
The international drugs watchdog estimated that anabolic steroids accounted for about 43 percent of positive results among athletes in 2005 with testosterone, nandrolone and stanozolol among the most prominent.
In the study, Schulze and her colleagues chose 55 men, of whom 15 percent had the important change in the UGT2B17 gene normally involved in the secretion of testosterone.
They injected each of them with a 360-milligram dose of testosterone and checked them for signs of suspicious levels of the male hormone over a 15-day period.
They found that the common variation could give rise to wildly different results, even when the dose was the same. The results were not skewed for people without the genetic change.
For example, six days after the injection when the testosterone levels are highest in urine, about 59 percent of people with the variation had a result officials would deem suspicious. That figure was 100 percent for those without the genetic advantage.
“Nearly half of the individuals in our study who carried this genetic variation would go undetected in a regular doping test after a single 360-milligram dose of testosterone,” Schulze said.
“If you don’t have the gene you don’t secrete testosterone in your urine.”
The genetic change was most common in the East Asian countries of Japan, Korea and China where about 65 percent of people carry the variation, Schulze said in a telephone interview.
For Caucasians and people of African descent the figure was 10 percent or less, she added.
The researchers plan to publish their findings in the Journal of Clinical Endocrinology & Metabolism in June.
More research was needed but one idea would be for genetic profiles of each athlete to be drawn up to determine what was the appropriate cut-off point for testosterone levels, Schulze said.
“When you talk about genetic variations, 10 percent is still quite a high number,” she said. “Current doping tests are based on people who do not have the genetic variation.”
Olympic authorities say they will carry out some 4,500 doping tests at August’s Beijing Games, up from 3,500 at the Athens Olympics four years ago.
Editing by Clare Fallon