High Dose Growth Hormone Exerts an Anabolic Effect at Rest and During Exercise in Endurance-Trained Athletes

J Clin Endocrinol Metab. 2003 Nov;88(11):5221-6. doi: 10.1210/jc.2002-021872.

Abstract

The anabolic actions of GH in GH-deficient adults and children are well documented. Replacement with GH in such individuals promotes protein synthesis and reduces irreversible loss of protein through oxidation. Although GH is known to be self-administered by athletes, its protein metabolic effects in this context are unknown. This study was designed to determine whether 4 wk of high dose recombinant human GH (r-hGH) administration altered whole body leucine kinetics in endurance-trained athletes at rest and during and after 30 min of exercise at 60% of maximal oxygen uptake. Eleven endurance-trained male athletes were studied, six randomized to receive r-hGH (0.067 mg/kg.d), and five to receive placebo. Whole body leucine turnover was measured at rest and during and after exercise, using a 5-h primed constant infusion of 1-[(13)C]leucine, from which rates of leucine appearance (an index of protein breakdown), leucine oxidation, and nonoxidative leucine disposal (an index of protein synthesis) were estimated. Under resting conditions, r-hGH administration increased rate of leucine appearance and nonoxidative leucine disposal, and reduced leucine oxidation (P < 0.01). This effect was apparent after 1 wk, and was accentuated after 4 wk, of r-hGH administration (P < 0.05). During and after exercise, GH attenuated the exercise-induced increase in leucine oxidation (P < 0.05). There were no changes observed in placebo-treated subjects compared with the baseline study. We conclude that GH administration to endurance-trained male athletes has a net anabolic effect on whole body protein metabolism at rest and during and after exercise.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Carbon Isotopes
  • Doping in Sports
  • Human Growth Hormone / administration & dosage*
  • Human Growth Hormone / adverse effects
  • Humans
  • Insulin-Like Growth Factor I / metabolism
  • Leucine / pharmacokinetics
  • Male
  • Oxygen Consumption / drug effects*
  • Oxygen Consumption / physiology
  • Physical Endurance
  • Physical Exertion / drug effects*
  • Physical Exertion / physiology
  • Rest / physiology
  • Sports
  • Thyroid Hormones / blood

Substances

  • Carbon Isotopes
  • Thyroid Hormones
  • Human Growth Hormone
  • Insulin-Like Growth Factor I
  • Leucine