Endocrine Abstracts

Performance enhancing substances enjoy considerable popularity among athletes, particularly if deemed undetectable. Doping with growth hormone has been considered undetectable until recently. Two strategies have been pursued to detect GH doping: Pharmacological endpoints and GH isoform composition.

For the former approach the consortium GH 2000/2004 has identified markers of GH action and found a combination of parameters from the IGF-system and collagen markers to provide a suitable combination to detect GH abuse. The latter approach is based on the molecular nature of isoform composition in which GH is released from the pituitary. Monomeric 22 kD hGH in its unbound form accounts only for approximately one quarter of all GH isoforms released into circulation. In contrast, the vast majority of hGH as derived from recombinant DNA technology is in the monomeric 22 kD form. We have therefore developed “differential immunoassay” strategy in which every sample is analysed twofold: The first assay preferentially recognises 22 kDa monomeric hGH while the second assay recognises the bulk of isoforms as released from the pituitary. Both assays are based on monoclonal antibodies selectively screened for their specificity characteristics. The 22 kD preferential antibody as well as the “permissive” antibody are immobilised and allowed to react with the sample before incubation with a common labelled anti-hGH antibody. The approach was tested by blinded samples and found capable of distinguishing pituitary-derived- from recombinant hGH. This test has been introduced in several WADA accredited laboratories and has been applied – without detecting positive cases – at the recent Summer Olympic Games in Athens.

The pharmacological marker test will be capable of detecting GH abuse in athletes for a longer period of time than the isoform approach, but may fail after initial GH injections. It can therefore be speculated, that both strategies will be pursued side by side in the future.