When accused of doping, many sportsmen and women claim innocence. And whereas most of them may be the cheats that the tests say they are, some may be completely innocent.
Over the last ten years, the anabolic steroid nandrolone has made headlines for all the wrong reasons. Sprinters like the 1992 Olympic 100 metre champion Linford Christie and Jamaican Merlene Ottey are just two of the high profile athletes to have tested positive.
The spate of positive tests in the late 1990s and early 2000s was widely attributed to the use of dietary supplements, and athletes were urged to be weary of which supplements they take.
Endogenous or exogenous
The difficulty with most forms of doping tests lies in distinguishing between chemicals produced by the athlete's body (endogenous), and chemicals from an external source (exogenous.)
More and more scientists are accepting that the body produces low levels of nandrolone metabolites. According to current International Olympic Committee rules, concentrations of a nandrolone metabolite above a certain threshold indicates exogenous use.
A person's nandrolone levels can be raised by a number of factors, including taking supplements or eating beef that contains high levels of nandrolone, pregnancy, and intense physical exertion.
But whereas scientists are well aware of these factors, the possibility exists that an unexpected, and as yet poorly understood, factor may also be pushing results over the thresholds and delivering false positives.
Injuries skewing results?
According to an, as yet unpublished, study by Prof. Mike Lambert and Dr Ryan Kohler, from the MRC/UCT research unit for exercise science and sports medicine, there may be a link between severe musculoskelital injury and raised levels of the nandrolone metabolite 19- norandrosterone (19-NA). It is this metabolite that is measured in nandrolone tests.
Their study followed the observation of a correlation between sports injuries and positive nandrolone tests. The most notable example of this is that of the former Springbok prop Cobus Visagie, who tested positive for nandrolone after sustaining a wrist bone fracture. Visagie was later cleared on a technicality.
In Lambert and Kohler's study, 32 healthy male subjects (18 to 50 years) who had sustained severe musculoskeletal injury were recruited. Urine samples were collected from the subjects within three hours of injury and again six weeks after the injury, and analysed for nandrolone metabolites.
31 of the 32 subjects tested negative. However, the 19-NA levels in the urine of the 32nd subject exceeded the acceptable limits set by the International Olympic Committee. Since it is extremely unlikely that the subject, a construction worker who was injured on the job, could have taken nandrolone exogenously, the result does seem to warrant further investigation.
The IOC defined a doping offence for nandrolone as a concentration of 19-NA in human urine exceeding 2 ng/ml in men and 5 ng/ml in women. The construction worker in the study had a 19-NA level of 2.8 ng/ml.
How it may work
The mechanism by which injury may raise levels of 19-NA is still unproven. But in another study, published in the British Journal of Sports Medicine, Lambert and Kohler speculate about how it may happen.
The theory relates to the idea that 19-NA is produced as an intermediary during the aromatisation (conversion) of testosterone to oestrogen – a theory that is also used to explain what seems to be the endogenous production of low levels of 19-NA in the human body.
The theory is that in certain cases injuries may trigger a similar chain reaction in which the aromatisation of adrenal androgens may cause levels of 19-NA to rise in a similar way.
Not all athletes are equal
A further factor that complicates testing for nandrolone, and doping tests more generally, is the fact that people's bodies are not all the same.
Genetic differences may impact on things like the aromatisation processes described above, and as a result may directly impact on 19-NA levels.
Furthermore, factors such as age and the amount of muscle and fat in a person's body may also have an impact. This, combined with fluctuations due to intense exercise and the possibility of injuries boosting 19-NA levels, certainly warrants further study.
In their article in the British Journal of Sports Medicine, Lambert and Kohler conclude that the IOC thresholds are still open to debate and that the possibility of false positives cannot be categorically denied. – (Marcus Low, Health24)
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