Scientists in California have discovered the brain circuitry that links deep sleep to the release of growth hormones, revealing why inadequate sleep hampers muscle recovery, metabolism, and cognitive functions. It has long been recognized that growth hormone is released during sleep, which is why athletes prioritize restful sleep for recovery and adolescents require ample sleep for growth. However, the underlying mechanisms governing this process have remained elusive.
The researchers found that two hormones in the hypothalamus regulate the release of growth hormone: GHRH (growth hormone-releasing hormone) promotes its release, while somatostatin inhibits it. Their studies revealed that during REM sleep, levels of both hormones increase, whereas during deep non-REM sleep, somatostatin levels decrease. This differentiation in sleep stages helps explain their varying effects on the body.
To investigate further, the team implanted electrodes in mice and used light to stimulate neurons in the hypothalamus, uncovering a previously unrecognized feedback loop. They found that sleep initiates the release of growth hormone, which in turn activates the locus coeruleus, a brain region that governs attention and alertness. Interestingly, when this region becomes overly active, the brain signals a return to sleep. According to the researchers, there is a delicate balance between sleep and growth hormone production: insufficient sleep can lead to decreased hormone levels, while excessive hormone release can push the brain towards wakefulness.
Given that growth hormone also plays a role in regulating glucose and fat metabolism, chronic sleep deprivation could heighten the risk of obesity, diabetes, and heart disease. Moreover, disturbances in the locus coeruleus have been associated with various neurological conditions, including Alzheimer's and Parkinson's diseases. This breakthrough could pave the way for new treatment strategies for these disorders.
Informational material. 18+.
