Sleep and endocrine changes after intranasal administration of growth hormone-releasing hormone in young and aged humans.
Level 2 - randomized trial
Double-blind randomized crossover trial in humans
PubMed 10451909 · doi:10.1016/s0306-4530(99)00027-x
What was done
In a double-blind crossover trial, 12 young and 11 older healthy men received either 300 µg of intranasal growth hormone-releasing hormone (GHRH) or placebo 30 minutes before bedtime at 23:00 h. Polysomnographic sleep was monitored until 07:00 h, and blood was drawn at 15-minute intervals to measure cortisol and growth hormone (GH) concentrations.
What was found
Intranasal GHRH reduced cortisol nadir concentrations during early sleep (P < 0.05) and reduced the sleep-induced surge in GH concentrations during early sleep. GHRH administration also increased rapid-eye-movement (REM) sleep and slow-wave sleep (SWS), concentrated in the second half of the sleep period. Effects did not differ by age group. The abstract reports no numerical values for sleep stage durations, GH levels, or exact effect sizes.
Why it matters
This study demonstrates that intranasal delivery of GHRH can centrally modulate both sleep architecture and neuroendocrine function in humans across age groups without requiring systemic injection.
Limits
The sample size is small (n = 23) and includes only healthy men, limiting generalizability to women or individuals with sleep disorders. Only a single acute dose was tested, and the abstract omits quantitative values and confidence intervals for most measured outcomes.
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