Serum IGF-I and IGF binding proteins 2 and 3 as potential markers of doping with human GH

IGF-I and IGF binding protein (IGFBP)-3 levels in man are positively regulated by GH status; in contrast, evidence suggests an inverse relationship between GH status and IGFBP-2. We investigated the effects of somatropin administration on the serum concentrations of these analytes, together with serum and urinary concentrations of GH, to evaluate their potential as markers in the development of a test for detecting doping with GH in sports competitors.

Somatropin was administered subcutaneously at a dose of 0.15 U/kg bodyweight/day at 1000 h for 3 days to eight healthy men (20-32 years old).

Serum concentrations of GH, IGF-I, IGFBP-2 and -3 were determined in blood samples collected at 1600 h on the days prior to (day -1), during (days 0, 1 and 2), and following administration (days 3 and 7). Urine was collected continuously from days -2 to 3 and then on day 7.

Serum and urinary concentrations of GH were only raised on the days of administration whereas, following cessation of somatropin, the increases in the serum concentrations of IGF-I and IGFBP-3 were sustained for at least 1 day (30 h). Serum IGFBP-2 decreased during the period of administration and was still suppressed on day 3. The concentration ratios of IGFBP-3 to IGFBP-2 and IGF-I to IGFBP-2 increased markedly with administration and both ratios were still significantly augmented compared with basal values 30 h after the last administration.

With acute administration of somatropin to healthy men the serum concentration of IGFBP-2 decreases and the ratios of serum IGF-I/ IGFBP-2 and IGFBP-3/IGFBP-2 increase. These ratios should be considered in the development of a test for detecting somatropin administration in sport.