Scientists have uncovered the brain mechanism that links sleep to the release of growth hormone, shedding light on a process essential for physical development, metabolism and brain function.
The study, conducted by researchers at the University of California, Berkeley and published in the journal Cell, identifies the neural circuits that control growth hormone secretion during sleep and explains how the brain maintains the balance between sleep and wakefulness.
Why growth hormone matters
Growth hormone plays a vital role in bone and muscle development, tissue repair, fat regulation and overall health.
Scientists have long known that growth hormone levels rise during sleep, particularly during deep non-REM sleep. However, until now, the brain mechanisms responsible for controlling this process had remained unclear.
The new findings explain how sleep actively regulates hormone release rather than simply coinciding with it.
Brain circuits behind sleep and hormone release
The research team, led by Professor Yang Dan, recorded the activity of neurons in the hypothalamus, an area of the brain involved in regulating many essential bodily functions.
The researchers identified neural circuits that control the release of growth hormone and discovered a feedback mechanism that helps maintain hormonal balance.
According to postdoctoral researcher Xinlu Ding, previous evidence linking sleep and growth hormone relied mainly on blood measurements.
By directly recording neural activity in mice, the team was able to observe how the brain controls hormone secretion, laying the groundwork for future therapeutic approaches.
Two hormones work differently during sleep
Using advanced circuit-mapping techniques, the researchers found that two hormones involved in regulating growth hormone—growth hormone-releasing hormone (GHRH) and somatostatin—behave differently depending on the stage of sleep.
During REM sleep, levels of both hormones increase, leading to greater growth hormone release. During non-REM sleep, somatostatin decreases while GHRH rises more moderately.
The findings reveal a complex regulatory system that adjusts hormone production throughout the sleep cycle.
A balance between sleep and wakefulness
The study also identified a feedback mechanism involving the locus coeruleus, a region of the brainstem associated with attention and alertness.
As growth hormone accumulates during sleep, it stimulates this area, helping promote wakefulness. However, excessive activity in the same brain region may have the opposite effect, contributing to sleepiness.
According to co-author Daniel Silverman, the findings suggest that sleep and growth hormone form a balanced system: insufficient sleep reduces growth hormone production, while excessive hormone activity helps shift the brain toward wakefulness.
Implications for future treatments
Researchers say the discovery could lead to new treatments for sleep disorders linked to metabolic diseases such as diabetes, as well as neurodegenerative conditions including Parkinson’s disease and Alzheimer’s disease.
The study also reinforces the importance of quality sleep, suggesting that growth hormone contributes not only to growth and muscle repair but also to cognitive function and alertness after waking.
