The endocrine system (the collection of glands that secrete hormones into the circulatory system and are carried to another organ) has a complex response to sleep57. The secretion of some hormones increases during sleep (e.g., growth hormone, prolactin, and luteinizing hormone), while the secretion of other hormones is inhibited (e.g., thyroid stimulating hormone and cortisol).
Some hormones are tied directly to a particularly sleep stage. Growth hormone is typically secreted in the first few hours after the onset of sleep and generally is released during slow-wave sleep (SWS). Cortisol is tied to the circadian rhythm, and peaks in late afternoon, regardless of the person’s sleep status or the darkness/light cycle. Melatonin is released in the dark and is suppressed by light58. Thyroid hormone secretion occurs in the late evening59.
Considerable research has linked endocrine dysfunction and sleep dysfunction (specifically insomnia)60. It has been proposed that over-activity (or hyper-drive) of the “hypothalamic-pituitary-adrenal” (HPA) axis, the over-activation of hormonal interaction between a part of the brain and the adrenal gland, can impact sleep function — perhaps in response to stress — and subsequently increase secretion of cortisol and norepinephrine, thus promoting wakefulness61.
Diabetes is a specific disease that affects the endocrine system’s ability to produce the hormone insulin and is, in turn, affected by sleep. Adults who report getting 5 or fewer hours of sleep a night were 2.5 times more likely to have diabetes, compared to people who sleep 7 - 8 hours per night. People who slept 6 hours/night were 1.7 times more likely to have diabetes than their peers who sleep longer. Interestingly, people who sleep for 9 or more hours also have higher rates of diabetes, so perhaps both insufficient sleep and too much sleep are both unhealthy when it comes to insulin and the development of diabetes62. Orexin plays an important role in glucose metabolism (including through its involvement in the production of a circadian glucose rhythm), preventing or promoting insulin resistance63 64.
57. Van Cauter E, Tasali E. Endocrine physiology in relation sleep and sleep disturbances. In: Kryger MH, Roth T, Dement WC, eds. Principles and practice of sleep disorders. 5th ed. Philadelphia: Elsevier and Saunders; 2011:291-311.
58. Buxon OM, Spiegel K, Van Cauter E. Modulation of endocrine function and metabolism by sleep and sleep loss. In: Lee-Chiong TL, Sateia MJ, Carskadon MA, eds. Sleep Medicine. Philadelphia, Pa: Hanley and Belfus; 2002:59-69.
59. Institute of Medicine (IOM) Committee on Sleep Medicine and Research, Colten HR and Altevogt BM (ed.), Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem, Washington, DC: National Academy of Sciences, 2006.
60. Institute of Medicine (IOM) Committee on Sleep Medicine and Research, Colten HR and Altevogt BM (ed.), Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem, Washington, DC: National Academy of Sciences, 2006.
61. Buckley TM, Schatzberg AF. On the interactions of the hypothalamic-pituitary-adrenal (HPA) axis and sleep: normal HPA axis activity and circadian rhythm, exemplary sleep disorders. J Clin Endocrinol Metab. 2005;90:3106-3114
62. Institute of Medicine (IOM) Committee on Sleep Medicine and Research, Colten HR and Altevogt BM (ed.), Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem, Washington, DC: National Academy of Sciences, 2006.
63. Messina G, Dalia C, Tafuri D, “Orexin A Controls Glucose Metabolism,” J Diabete Metab 2014; 5(7): 398. doi:10.4172/2155-6156.1000398
64. Tsuneki H, Tokai E, Nakamura Y, “Hypothalamic orexin prevents hepatic insulin resistance via daily bidirectional regulation of autonomic nervous system in mice,” Diabetes 2015;64(2):459-70. doi: 10.2337/db14-0695. Epub 2014 Sep 23.