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Data support ‘biological passport’ for GH doping
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Biomarkers of growth hormone are not subject to the same natural fluctuations as growth hormone itself, which could potentially help sporting authorities worldwide catch athletes who use it illegally to boost their performance, new research suggested.
Data indicate that levels of insulin-like growth factor I and type 3 procollagen may create an individual athlete biological passport to help provide clearer, personalized results.
Researchers compared data from four separate studies that measured blood serum levels of IGF-I and type 3 procollagen in 303 elite athletes and 78 amateur athletes aged 17 to 53 years during a period of up to 12 months. Previous data from the GH-2000 and GH-2004 studies identified IGF-I and type 3 procollagen as good biomarkers of GH doping because blood levels of these substances change significantly when GH is injected but not after exercise.
According to the results, intra-individual variation of biomarker concentrations and GH-2000 scores are much lower than inter-individual variation.
The researchers found that levels of IGF-I, type 3 procollagen and the GH-2000 score, which was calculated from levels of IGF-I and type 3 procollagen, varied between athletes (inter-individual variability of IGF-I: 44% to 71%; type 3 procollagen: 31% to 58%; GH-2000 scores: over 3 units). However, these values were only modestly different in a single individual during the athletic season (intra-individual variability of IGF-I: 14% to 16%; type 3 procollagen: 7% to 18%; GH-2000 scores: under 0.6 units).
No athlete tested positive for GH during any of the studies.
“Our results show that the levels of the GH-dependent biomarkers IGF-I and type 3 procollagen within any individual remain relatively constant over time regardless of whether that person is an amateur or professional athlete,” Richard Holt, MD, of the developmental origins of health and disease division at the University of Southampton School of Medicine, said in a press release.
“This means that they might be logged into an individual ‘athlete biological passport’ to establish an individual’s normal GH-2000 score, against which future tests can be compared,” Holt said. “The principle of the athlete biological passport is that the athlete is his or her own benchmark, which increases the specificity of the test and helps us catch more cheaters.”
Future research is needed to establish guidelines to calculate a concrete scoring method that would differentiate between GH abuse and a normal GH-2000 score, the researchers concluded.
Holt RIG. Clin Endocrinol. 2010:72;520-526.