Circadian system, sleep and endocrinology.
Summary of "Circadian system, sleep and endocrinology."
Levels of numerous hormones vary across the day and night. Such fluctuations are not only attributable to changes in sleep/wakefulness and other behaviors but also to a circadian timing system governed by the suprachiasmatic nucleus of the hypothalamus. Sleep has a strong effect on levels of some hormones such as growth hormone but little effect on others which are more strongly regulated by the circadian timing system (e.g., melatonin). Whereas the exact mechanisms through which sleep affects circulating hormonal levels are poorly understood, more is known about how the circadian timing system influences the secretion of hormones. The suprachiasmatic nucleus exerts its influence on hormones via neuronal and humoral signals but it is now also apparent that peripheral tissues contain circadian clock proteins, similar to those in the suprachiasmatic nucleus, that are also involved in hormone regulation. Under normal circumstances, behaviors and the circadian timing system are synchronized with an optimal phase relationship and consequently hormonal systems are exquisitely regulated. However, many individuals (e.g., shift-workers) frequently and/or chronically undergo circadian misalignment by desynchronizing their sleep/wake and fasting/feeding cycle from the circadian timing system. Recent experiments indicate that circadian misalignment has an adverse effect on metabolic and hormonal factors such as circulating glucose and insulin. Further research is needed to determine the underlying mechanisms that cause the negative effects induced by circadian misalignment. Such research could aid the development of novel countermeasures for circadian misalignment.
Affiliation
Division of Sleep Medicine, Brigham and Women's Hospital, Boston, MA, United States. cjmorris@rics.bwh.harvard.edu
Journal Details
This article was published in the following journal.
Name: Molecular and cellular endocrinology
ISSN: 1872-8057
Pages: 91-104
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/21939733
- DOI: http://dx.doi.org/10.1016/j.mce.2011.09.003
Medical and Biotech [MESH] Definitions
Sleep Disorders, Circadian Rhythm
Dyssomnias associated with disruption of the normal 24 hour sleep wake cycle secondary to travel (e.g., JET LAG SYNDROME), shift work, or other causes.
Dyssomnias
A broad category of sleep disorders characterized by either hypersomnolence or insomnia. The three major subcategories include intrinsic (i.e., arising from within the body) (SLEEP DISORDERS, INTRINSIC), extrinsic (secondary to environmental conditions or various pathologic conditions), and disturbances of circadian rhythm. (From Thorpy, Sleep Disorders Medicine, 1994, p187)
Circadian Clocks
Biological mechanism that controls CIRCADIAN RHYTHM. Circadian clocks exist in the simplest form in cyanobacteria and as more complex systems in fungi, plants, and animals. In humans the system includes photoresponsive RETINAL GANGLION CELLS and the SUPRACHIASMATIC NUCLEUS that acts as the central oscillator.
Delta Sleep-inducing Peptide
A nonapeptide that is found in neurons, peripheral organs, and plasma. This neuropeptide induces mainly delta sleep in mammals. In addition to sleep, the peptide has been observed to affect electrophysiological activity, neurotransmitter levels in the brain, circadian and locomotor patterns, hormonal levels, psychological performance, and the activity of neuropharmacological drugs including their withdrawal.
Hypersomnolence, Idiopathic
A sleep disorder of central nervous system origin characterized by prolonged nocturnal sleep and periods of daytime drowsiness. Affected individuals experience difficulty with awakening in the morning and may have associated sleep drunkenness, automatic behaviors, and memory disturbances. This condition differs from narcolepsy in that daytime sleep periods are longer, there is no association with CATAPLEXY, and the multiple sleep latency onset test does not record sleep-onset rapid eye movement sleep. (From Chokroverty, Sleep Disorders Medicine, 1994, pp319-20; Psychiatry Clin Neurosci 1998 Apr:52(2):125-129)
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