Effects of a growth hormone pulse on total and forearm substrate fluxes in humans

Am J Physiol. 1990 Jan;258(1 Pt 1):E86-91. doi: 10.1152/ajpendo.1990.258.1.E86.


Under physiological circumstances growth hormone (GH) is secreted in bursts after the onset of sleep and a few hours postprandially. Because most relevant studies have employed constant or repeated infusion of high doses of GH, the possible metabolic effects of such bursts are largely unknown. We have studied seven healthy, male subjects for 7 h after an intravenous bolus of 1) 140 micrograms GH and 2) saline. When injected, serum GH rose to a peak of 21 +/- 3 micrograms/l 10 min after injection. GH caused 1) a rapid, sustained 55% decrease in forearm glucose uptake (P less than 0.05) followed by increases toward control values, 2) a delayed 5 mg/100 ml decrease in plasma glucose (P less than 0.05), and 3) significant 60-250% increases (P less than 0.05) in all measured lipid intermediates (nonesterified fatty acids, 3-hydroxybutyrate, and glycerol) 120-160 min after administration followed by decreases to below control values (P less than 0.05). GH did not influence circulating levels of insulin, C-peptide, glucagon, or insulin-like growth factor I (IGF-I), or isotopically determined glucose turnover. Physiological bursts of GH secretion appear to have acute insulin antagonistic effects with maximal effect on lipolysis after 2 h. These effects are reversed after 4 h. Therefore, GH could play a key role in regulation of diurnal rhythms of substrate levels and fuel utilization in humans.

MeSH terms

  • 3-Hydroxybutyric Acid
  • Adult
  • Analysis of Variance
  • Blood Glucose / metabolism
  • C-Peptide / blood*
  • Fatty Acids, Nonesterified / blood
  • Forearm / blood supply
  • Glucagon / blood*
  • Glycerol / blood
  • Growth Hormone / administration & dosage
  • Growth Hormone / blood
  • Growth Hormone / pharmacology*
  • Humans
  • Hydroxybutyrates / blood
  • Injections, Intravenous
  • Insulin / blood*
  • Kinetics
  • Male
  • Regional Blood Flow / drug effects
  • Time Factors


  • Blood Glucose
  • C-Peptide
  • Fatty Acids, Nonesterified
  • Hydroxybutyrates
  • Insulin
  • Growth Hormone
  • Glucagon
  • Glycerol
  • 3-Hydroxybutyric Acid