T. Karila et al., GROWTH-HORMONE INDUCED INCREASE IN SERUM IGFBP-3 LEVEL IS REVERSED BYANABOLIC-STEROIDS IN SUBSTANCE-ABUSING POWER ATHLETES, Clinical endocrinology, 49(4), 1998, pp. 459-463
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.