Deep sleep doesn’t just make you feel rested. It actively rebuilds the body, strengthens muscles, supports bone growth and helps burn fat. For teenagers, it is also essential to reach their full height potential.
At the heart of all this is growth hormone, which surges during sleep. But scientists have long been puzzled as to why sleep deprivation, especially the early deep stage known as non-REM sleep, leads to decreased levels of this important hormone.
Scientists discover the brain circuit behind it
Researchers at the University of California, Berkeley have revealed the answer. In a study published in the journal Cell, they mapped the brain circuits that control growth hormone release during sleep and identified a new feedback system that keeps their levels balanced.
This discovery provides a clearer understanding of how sleep and hormones work together. It could also open the door to new treatments for sleep disorders associated with metabolic diseases such as diabetes and neurological diseases such as Parkinson’s and Alzheimer’s.
“People know that growth hormone release is closely related to sleep, but only by taking blood samples during sleep and checking growth hormone levels,” said Xinlu Ding, lead author of the study and a postdoctoral fellow in the Department of Neuroscience and Helen Wills Neuroscience Institute at the University of California, Berkeley. “We’re actually directly recording neural activity in mice to see what’s going on. We’re providing the basic circuitry that we can work towards developing a variety of treatments in the future.”
Lack of sleep doesn’t just leave you feeling tired. Because growth hormone helps control how your body processes sugar and fat, lack of sleep can increase your risk of obesity, diabetes, and heart disease.
Brain areas that drive growth hormone
The system behind this process is buried deep in the hypothalamus, an ancient part of the brain that all mammals share. Here, specialized neurons release signals that induce or suppress growth hormone.
The two main players are growth hormone-releasing hormone (GHRH), which stimulates its release, and somatostatin, which inhibits it. Together, they regulate hormonal activity throughout the sleep-wake cycle.
When growth hormone enters the body, it activates the locus coeruleus, a brainstem region that controls attention, alertness, and cognitive function. Disorders in this area are associated with a wide range of neurological and psychiatric disorders.
“Understanding the neural circuitry of growth hormone release may ultimately lead to new hormonal therapies that improve sleep quality and restore normal growth hormone balance,” said study co-author Daniel Silverman, a postdoctoral fellow at the University of California, Berkeley. “There are several experimental gene therapies that target specific cell types. This circuit could be a new handle for reducing excitability in the locus coeruleus, which has not been talked about until now.”
How sleep stages control hormone release
To study this system, the researchers recorded brain activity in mice by inserting electrodes and stimulating neurons with light. Because mice sleep for short periods throughout the day and night, they were able to closely observe how growth hormone changes during each sleep stage.
The researchers found that GHRH and somatostatin behave differently depending on whether the brain is in REM or non-REM sleep.
Both hormones increase during REM sleep, leading to a surge in growth hormone. During NREM sleep, somatostatin decreases, but GHRH increases more modestly, still increasing hormone levels, but in a different pattern.
Amazing feedback loops in the brain
Researchers also discovered a feedback loop linking growth hormone and arousal. As you sleep, growth hormone gradually accumulates and stimulates the locus coeruleus, prompting your brain to wake up.
But there’s a twist. If this brain region becomes too active, it can actually cause drowsiness, creating a delicate balance between sleep and wakefulness.
“This suggests that sleep and growth hormone form a tightly balanced system. Too little sleep can reduce the release of growth hormone, and too much growth hormone can conversely push the brain toward a state of wakefulness,” Silverman said. “Sleep promotes the release of growth hormone, which feeds back to regulate wakefulness. This balance is essential for growth, repair, and metabolic health.”
Why is it important for your brain and body?
This balance not only affects physical growth; Because growth hormone acts through brain systems that control attention, it can also affect how clearly you think and how focused you feel.
“Growth hormone not only helps build muscle and bone and reduce fat tissue, but it also promotes your overall level of alertness when you wake up and may have benefits for cognitive function,” Ding said.
Funding and research team
This research was supported by the Howard Hughes Medical Institute (HHMI) and the Pivotal Life Sciences Chancellor’s Chair Fund. Yang Dan holds the Life Sciences Dean’s Chair, which is pivotal to the field of neuroscience. The study also included collaborators from the University of California, Berkeley and Stanford University.
