Hormones and metabolism

Sleep is the time when the body secretes many important hormones that affect growth, regulate energy, and control metabolic and endocrine functions. For example, blood levels of the stress hormone, cortisol, which can promote wakefulness, increase near the end of a complete sleep cycle. Growth hormone, which contributes to childhood growth and helps regulate muscle mass in adults, also is secreted during sleep. Follicle stimulating hormone and luteinizing hormone, both involved in reproduction, also are released during sleep; the sleep-dependent release of luteinizing hormone is thought to initiate puberty. Further, the sleep cycle affects secretion of hormones influencing appetite and weight.

Sleep loss has powerful potential implications for obesity and diabetes, both of which have grown to epidemic proportions in recent years.