ANABOLIC EFFECTS OF GROWTH-HORMONE IN OBESE DIET-RESTRICTED SUBJECTS ARE DOSE DEPENDENT

In previous studies growth hormone (GH) injections [0.1 mg/kg ideal body wt (IBW) every other day] produced significant increases in plasma insulin-like growth factor I (IGF-I) concentrations and nitrogen retention, which were attenuated when 12 kcal/kb IBW was ingested. The present study was done to determine whether doubling the GH dose would enhance its anabolic effects and facilitate fat loss. Eight women (33-83% over IBW) were fed 12 kcal/kg IBW for 14 wk. They received GH or vehicle injections, each for 5 wk during either weeks 2-6 or 9-13. GH improved nitrogen balance (GH, 3.6 ± 123.2 mmol/d; vehicle, -132.0 ± 117.9 mmol/d; x̄ ± SD; p < 0.001). Plasma IGF-I increased from 32.1 ± 9.6 to 79.4 ± 22.1 nmol/L by day 5 of GH (p < 0.001) and remained elevated until GH injections were discontinued. No significant effect of GH on mean body fat loss was observed. GH can induce significant anabolic responses even when caloric intake is decreased to 12 kcal/kg IBW. The degree and duration of these anabolic responses are dependent on the GH dose given.