A FEW months ago it was on nobody鈥檚 radar. Now tetrahydrogestrinone, or THG, is the talk of sports commentators the world over.
As New 杏吧原创 went to press, four American athletes and Britain鈥檚 fastest sprinter, Dwain Chambers, had tested positive for the substance. A federal grand jury is investigating BALCO, a nutritional supplements firm from the San Francisco area, and has subpoenaed a number of America鈥檚 best-known athletes. BALCO is denying allegations that it concocted and distributed the drug.
Meanwhile, in anti-doping labs across the world scientists are gingerly taking racks of supposedly 鈥渃lean鈥� urine samples out of their freezers and wondering whether to start testing them for traces of the substance. Even allowing for the hype of the ebullient US anti-doping officials who uncovered the evidence, it is clear that this could turn into the biggest doping expos茅 in sporting history.
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However many, or few, athletes turn out to be involved, the episode serves as a wake-up call for scientists and officials struggling to control doping. The American team behind the THG discovery was only able to go looking for the steroid because an anonymous whistleblower sent officials a syringeful of it. Without this tip-off no new drug 鈥� or scandal 鈥� would have been uncovered.
The episode underlines how reactive and full of gaps dope testing remains. Take the crucial question of sample storage. The THG positives were obtained by re-testing stored urine samples, and the outcome lends weight to the idea of making retroactive testing central to doping control. Athletes are likely to be deterred even from taking substances that are currently undetectable if they know that samples may be retested months or years later when new tests become available.
But just how long is it safe to keep urine or blood samples in the freezer before any illegal substances in them begin to degrade? Different labs have been keeping samples for different lengths of time. Some anti-doping scientists dismiss the idea of keeping samples for more than a few months; others say it is possible to get legitimate results from samples frozen for years. Clearly more research is needed here.
Another key message is that anti-doping labs are going to have to expand the range of tests they employ if they are to remain credible. To date dope testing has relied chiefly on narrow forms of chemical analysis using, for example, mass spectrometry. Urine, and occasionally blood, samples are screened for particular substances with specific chemical structures. The problem with these tests is that they generally only work when the machines know what they are looking for. Small chemical modifications of well-known, easy-to-detect doping agents can render the substances invisible, unless or until officials get a tip-off.
For this reason, some experts believe that traditional chemical screening should be supplemented by more sophisticated tests capable of detecting the knock-on effects of drugs on an athlete鈥檚 physiology.
It has been known for years that when most active steroids and peptide hormones are taken as supplements they will alter levels of certain proteins in the body, or patterns of gene activity in muscle or other tissues. The tools of molecular biology are now advanced enough to enable scientists to map these proteins and gene activities in intricate detail. And with this detail, say scientists who back the approach, will come the power to say which patterns result from vigorous exercise and nutritional programmes and which from drugs. Such tests would certainly make 鈥渕asking鈥� much harder to achieve. Minor modifications to drugs made solely with the aim of fooling mass spectrometers would be unable to conceal the substances鈥� full impact on an athlete鈥檚 physiology.
Is the approach realistic? The World Anti-Doping Agency is already funding work in this area, and a number of teams are already attempting to use gene expression or protein levels as the basis of a long-awaited test for human growth hormone, which is already on the list of banned substances. Officials on the International Olympic Committee met this week to review the findings of these studies. The outcome of their discussions could tell us whether anti-doping science will remain wedded to the chemical techniques of the past, or chart a new course that embraces the brave new age of molecular biology.