Scientists Discover How Sleep Triggers Growth Hormone Through a Brain Circuit

Scientists have long known that sleep and growth hormone are closely connected. Growth hormone release increases during sleep, particularly during deeper stages, but exactly how the brain controls this relationship has remained unclear.

Now, researchers at the University of California, Berkeley have mapped a neural circuit in mice that helps explain how sleep regulates growth hormone release — and how the hormone may, in turn, influence the brain systems responsible for wakefulness. The study was published in Cell in September 2025.

The discovery provides a more detailed picture of the communication between the brain’s sleep-regulating systems and the hormonal system responsible for growth hormone.

Two Signals Act Like an Accelerator and a Brake

At the centre of the mechanism are two signalling systems in the hypothalamus: growth hormone-releasing hormone (GHRH) and somatostatin.

GHRH promotes growth hormone release, while somatostatin inhibits it. Together, they help regulate when and how much growth hormone is released.

Researchers studied the activity of these neural circuits in sleeping and awake mice and found that their behaviour changes depending on the stage of sleep.

During non-REM sleep, somatostatin activity decreases while GHRH increases moderately. This combination favours greater growth hormone release.

The researchers also observed different patterns during REM sleep, showing that growth hormone regulation is not simply an on-or-off process controlled by sleep.

The Brain Appears to Have a Feedback System

The most interesting part of the discovery may be what happens after growth hormone is released.

The researchers found that growth hormone affects neurons in a brainstem region called the locus coeruleus. This region plays an important role in arousal, attention and wakefulness.

The findings suggest a feedback mechanism: sleep promotes growth hormone release, while increasing growth hormone activity can influence the neural system involved in wakefulness.

In other words, the relationship appears to work in both directions.

Sleep → growth hormone → brainstem activity → regulation of wakefulness

This may help explain how the brain maintains a balance between staying asleep and eventually becoming ready to wake.

Why Growth Hormone Matters

Growth hormone is widely associated with childhood growth, but its functions extend well into adulthood.

It contributes to processes involving muscle and bone maintenance, metabolism and tissue repair. UC Berkeley researchers note that growth hormone also plays an important role in glucose and fat metabolism.

This is one reason why sleep disruption can have consequences beyond simply feeling tired the next morning.

However, the new study does not show that one particular amount of sleep or one specific number of hours automatically produces a particular amount of growth hormone in humans.

The experiment was performed in mice, and researchers caution that the precise implications for human sleep and recovery still need to be established.

What Happens During Non-REM Sleep?

Non-REM sleep is particularly interesting because it includes the deeper stages of sleep associated with important physiological processes.

The Berkeley researchers found that the hormonal circuit behaves differently during non-REM and REM sleep. During non-REM sleep, the reduction in somatostatin combined with a moderate increase in GHRH favoured growth hormone release.

This provides a possible explanation for an observation scientists have made for decades: growth hormone levels are strongly linked to sleep.

Until now, much of that understanding came from measuring hormone levels in blood.

The new research goes deeper by looking directly at the neural circuitry controlling the process.

Researchers Actually Recorded Brain Activity

The team, led by neuroscientist Yang Dan, used advanced neuroscience techniques to study the circuits involved.

Researchers recorded neural activity in mice and stimulated specific neurons in the hypothalamus to observe how the sleep state and growth hormone system responded. They also used circuit-tracing techniques to identify connections between the relevant brain regions.

That allowed them to move beyond simply asking when growth hormone increases.

They could begin asking a more fundamental question:

Which neurons are responsible for making it happen?

This distinction is important because identifying a biological circuit can eventually give researchers potential targets for future therapies.

Could This Help Explain Sleep Disorders?

The researchers believe the findings could eventually contribute to new approaches for understanding or treating conditions involving sleep, metabolism and hormonal regulation.

UC Berkeley researchers specifically pointed to potential relevance for sleep disorders and metabolic conditions such as diabetes, while also noting possible connections to neurological diseases.

But it is too early to turn the discovery into a treatment recommendation.

The study describes a mechanism in mice. Translating that mechanism into human medicine will require additional research to determine whether the same circuit operates in humans in the same way.

A Mattress Cannot Produce Growth Hormone

One important distinction is worth making.

A comfortable mattress or sleep environment cannot directly create growth hormone.

What a good sleep environment can do is help remove some of the obstacles that interfere with sleep — such as discomfort, excessive noise or inconsistent sleeping conditions.

The biological process itself is controlled by the brain and endocrine system.

The new study helps explain that process at a much deeper level.

The Bigger Picture

The discovery shows that sleep is not simply a period when the brain switches off.

While we sleep, complex neural and hormonal processes continue operating.

The brain is regulating hormones, monitoring internal conditions and maintaining a carefully controlled balance between sleep and wakefulness.

Growth hormone is one part of that system.

The UC Berkeley findings suggest that the relationship between sleep and growth hormone is a two-way biological conversation rather than a simple sequence in which sleep causes the hormone to rise.

The research also highlights why scientists continue to study sleep as a fundamental biological process rather than treating it merely as rest.

There is still much to learn about whether the same circuit operates in humans, how it changes with age and how disruptions to the system might contribute to disease.

For now, one thing is becoming increasingly clear:

When we sleep, the brain is still working — and some of its most important work may be happening at the intersection of sleep, hormones and recovery.