GROWTH-HORMONE INDUCED INCREASE IN SERUM IGFBP-3 LEVEL IS REVERSED BYANABOLIC-STEROIDS IN SUBSTANCE-ABUSING POWER ATHLETES

OBJECTIVE Body builders may use growth hormone (GH) and anabolic stero ids to increase fitness and muscle mass. GH increases serum concentrat ions of IGF-I and IGFBP-3. The combined effects of GH and anabolic and rogenic steroids on IGFBP-3 and IGF-I levels are not known under authe ntic substance-abusing conditions. The aim of this study was to invest igate this in substance-abusing power athletes. DESIGN AND PATIENTS Ni ne healthy, non-obese and non-competing male power athletes, alt aggre ssive substance abusers, used GH and/or anabolic steroids independentl y of this study, Brood samples were taken both during and between the drug intake. Sixteen substance non-abusing wrestlers served as control s, MEASUREMENTS Serum IGF-I concentration was measured by radioimmunoa ssay and the IGFBP-3 concentration was measured by two immunofluoromet ric assays, one detecting proteolytic fragments of IGFBP-3. The capaci ty of serum to proteolytically cleave IGFBP-3 was studied by the prote olysis assay. RESULTS While growth hormone increased the IGFBP-3 and I GF-I concentrations, anabolic steroids decreased the same. Concomitant use of growth hormone and anabolic steroids decreased the IGFBP-3 con centration in five out of six abuse periods in spite of the fact that the IGF-I concentration remained elevated in four of them. However, in two men who were on low calorie diet both the IGF-I and IGFBP-3 conce ntrations decreased during combined GH/anabolic steroid abuse. No prot eolytic fragmentation of IGFBP-3 was observed. CONCLUSION Massive abus e of anabolic steroids decreases both the basal and GH-stimulated IGFB P-3 concentrations, whereas its effects on serum IGF-I concentration a re variable and affected by low calorie diet. This study demonstrates that detection of GH doping by measuring the IGF-I and/or IGFBP-3 leve ls has notable confounding factors.