Negative feedback suppression of sleep-related growth hormone secretion

Previous studies have demonstrated that injections of growth hormone (GH) can blunt subsequent GH secretory responses to daytime pharmacological stimulation. The current study was undertaken to determine whether GH administration to normal subjects would suppress sleep-related secretion. GH (2 U im) was given nine times over 5 days to each of six subjects, and sleep studies with blood sampling were performed 6 h after the last injection. Secretion during the first 2 h of sleep was decreased by 62.4%, indicating that sleep-related GH secretion may be responsive to a negative-feedback mechanism.