Body composition response to exogenous GH during training in highly conditioned adults.
The effects of biosynthetic methionyl-human growth hormone (met-hGH) on body composition and endogenous secretion of growth hormone (GH) and insulin-like growth factor I (IGF-I) were studied in eight well-trained exercising adults between 22 and 33 yr of age. By the use of double-blind procedures, met-hGH (2.67 mg/0.5 ml diluent, 3 days/wk) and bacteriostatic water (placebo, 0.5 ml, 3 days/wk) were administered in a repeated-measures design that counterbalanced treatment order. Duration of each treatment was 6 wk. Subjects trained with progressive resistance exercise throughout and were maintained on a high-protein diet monitored by extensive compositional analyses of daily dietary intake records. Hydrodensitometry revealed that met-hGH significantly decreased percent body fat (%fat) and increased fat-free weight (FFW) and FFW/fat weight (FW), whereas the placebo treatment did not change any of these measures. Changes in FFW/FW correlated with the relative dose of met-hGH but did not correlate with either the peak GH response to L-dopa/arginine stimulation or IGF-I levels obtained after treatment with placebo. There were no differences between treatments in the dietary intakes of total kilocalories, protein, carbohydrates, and fat. Mean IGF-I levels were elevated after treatment with met-hGH compared with postplacebo levels. After treatment with met-hGH, five of seven subjects had a suppressed GH response to stimulation from either L-dopa/arginine or submaximal exercise. We conclude that supraphysiological doses of met-hGH will alter body composition in exercising adults in a relative dose-dependent manner and that such treatment may suppress endogenous release of GH in some individuals.
Crist
D M
DM
Department of Medicine, University of New Mexico School of Medicine, Albuquerque 87131.
Peake
G T
GT
Egan
P A
PA
Waters
D L
DL
D000273:Adipose Tissue / Q000187:drug effects*; D000328:Adult; D001823:Body Composition / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D004311:Double-Blind Method; D015444:Exercise; D005260:Female; D013006:Growth Hormone / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000097:blood; D008297:Male; D010809:Physical Fitness; D011994:Recombinant Proteins / Q000494:pharmacology
D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone