Growth hormone induced increase in serum IGFBP-3 level is reversed by anabolic steroids in substance abusing power athletes.

OBJECTIVE

Body builders may use growth hormone (GH) and anabolic steroids to increase fitness and muscle mass. GH increases serum concentrations of IGF-I and IGFBP-3. The combined effects of GH and anabolic androgenic steroids on IGFBP-3 and IGF-I levels are not known under authentic substance-abusing conditions. The aim of this study was to investigate this in substance-abusing power athletes.

DESIGN AND PATIENTS

Nine healthy, non-obese and non-competing male power athletes, all aggressive substance abusers, used GH and/or anabolic steroids independently of this study. Blood samples were taken both during and between the drug intake. Sixteen substance non-abusing wrestlers served as controls.

MEASUREMENTS

Serum IGF-I concentration was measured by radioimmunoassay and the IGFBP-3 concentration was measured by two immunofluorometric assays, one detecting proteolytic fragments of IGFBP-3. The capacity of serum to proteolytically cleave IGFBP-3 was studied by the proteolysis assay.

RESULTS

While growth hormone increased the IGFBP-3 and IGF-I concentrations, anabolic steroids decreased the same. Concomitant use of growth hormone and anabolic steroids decreased the IGFBP-3 concentration 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 concentrations decreased during combined GH/anabolic steroid abuse. No proteolytic fragmentation of IGFBP-3 was observed.

CONCLUSION

Massive abuse of anabolic steroids decreases both the basal and GH-stimulated IGFBP-3 concentrations, whereas its effects on serum IGF-I concentration are variable and affected by low calorie diet. This study demonstrates that detection of GH doping by measuring the IGF-I and/or IGFBP-3 levels has notable confounding factors.