Evidence against a role for the growth hormone-releasing peptide axis in human slow-wave sleep regulation

Am J Physiol. 1998 May;274(5):E779-84. doi: 10.1152/ajpendo.1998.274.5.E779.


A complex interrelationship exists between sleep and somatotropic activity. In humans, intravenous injections of growth hormone-releasing hormone (GHRH) given during sleep consistently stimulate slow-wave (SW) sleep, particularly when given in the latter part of the night. In the present study, the possible somnogenic effects induced under similar conditions by GH-releasing peptide (GHRP) were investigated in seven young healthy men. Bolus intravenous injections of GHRP-2 (1 microgram/kg body wt) or saline, in randomized order, were given after 60 s of the third rapid-eye-movement period. All GHRP injections were immediately followed by transient prolactin elevations and by GH pulses of a magnitude within or around the upper limit of the physiological range. Except for a nonsignificant tendency to increased amounts of wakefulness during the 1st h after the injection, no effects of GHRP-2 administration on sleep were detected. There was in particular no enhancement of SW sleep. Thus, in contrast to GHRH, late-night single injections of GHRP-2 at a dosage resulting in similar GH elevations have no stimulatory effects on SW sleep. The present data provide evidence against the involvement of the GHRP axis in human SW sleep regulation.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Dose-Response Relationship, Drug
  • Drug Administration Schedule
  • Human Growth Hormone / blood
  • Humans
  • Injections, Intravenous
  • Male
  • Oligopeptides / administration & dosage
  • Oligopeptides / pharmacology*
  • Sleep / drug effects*
  • Sleep Stages / drug effects


  • Oligopeptides
  • Human Growth Hormone
  • growth hormone-releasing peptide-2