Endocrine Abstracts (2009) 19 P209

The effect of age on insulin-like growth factor-I and pro-collagen type III N-terminal peptide in elite adolescent athletes and its influence on the detection of growth hormone abuse

N Guha1, I Erotokritou-Mulligan1, J Brigg1, C Burford1, T Drake1, G Strobridge1, E Bassett2, D Cowan3, C Bartlett3, P Sonksen1 & R Holt1

1University of Southampton, Southampton, UK; 2University of Kent, Kent, UK; 3Kings College, London, UK.

Introduction: Using discriminant analysis, a method based on two growth hormone (GH) dependent markers, insulin-like growth factor-I (IGF-I) and pro-collagen type III N-terminal peptide (P-III-P) has been devised to detect exogenously administered GH. It is believed that GH is a popular substance of abuse amongst adolescent athletes. As previous studies on the detection of GH abuse involved predominantly adult athletes, it is necessary to validate the method in adolescent athletes.

Objectives: To examine serum IGF-I and P-III-P concentrations in elite adolescent athletes and to determine whether the method developed in adults can be used to detect GH abuse in this population.

Methods: One hundred and fifty-seven (85 male, 72 female) elite adolescent athletes aged between 12 and 20 years were recruited. Subjects represented 16 sporting disciplines. Blood samples were collected from each athlete either before or immediately after exercise. Serum IGF-I and P-III-P were measured by radioimmunoassay methods and the results were combined to calculate a discriminant function score for each athlete. The study received ethical approval from the local ethics committee.

Results: In male and female adolescent athletes, the mean serum IGF-I concentration was observed to rise in the early teenage years and then decline. In males, the mean serum P-III-P concentration demonstrated a similar pattern. Mean P-III-P concentration in female athletes declined from the age of 13 years onwards. None of the adolescent athletes in this study had discriminant function scores in excess of 3.7 (the proposed cut-off that suggests doping with GH in adult athletes).

Conclusions: Both IGF-I and P-III-P rise to a peak in puberty, which is earlier in girls than boys. We have found no evidence that the proposed GH-2000 score limit developed in adults would lead to an unacceptable rate of false positives.