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Biological Actions of Melatonin: Sleep and Jet Lag

المؤلف:  Norman, A. W., & Henry, H. L.

المصدر:  Hormones

الجزء والصفحة:  3rd edition , p358

2026-05-23

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The clearest and most important role of melatonin in the human is the one it plays in influencing, in partnership with the retina and the SCN, circadian rhythms throughout the body. In the SCN, where the central clock in the SCN has an autonomous period of slightly longer than 24 hours, the feedback effect of melatonin on SCN firing helps maintain entrainment of the central clock to the external light/dark cycle. It is now known that many peripheral cells have their own internal oscillators and melatonin is important in helping to synchronize many of these with the light/ dark cycle.

In humans, who are characteristically active by day and at rest during the night, manifestations of disruption of the normal circadian rhythm occur when an individual travels through several time zones, a condition known as “jet lag.” Fatigue, sleep problems, and reduced performance are common symptoms of jet lag. People who alternate between day and night shifts of work and are, therefore, exposed to light of 480 nm at night, also experience these symptoms. After the initial disturbance (travel or shift change), it can take several days for endogenous rhythms and environmental cues to become synchronized again. Exogenous melatonin can be effective in accelerating the phase shift if given at the appropriate time prior to bedtime at the destination. In the many studies of sleep, both involving jet lag and not, little to no association has been found between melatonin on either the stages or the duration of sleep.

The role of melatonin in sleep disorders is an area of great interest. In advanced (ASPS) or delayed (DSPS) sleep phase syndrome, patients either sleep during the day and wake in the middle of the night or do not sleep until the middle of the night. ASPS is often seen in elderly individuals and DSPS in children with some neurodevelopmental disorders. In both of these settings, restoring the melatonin during the night with controlled release hormone improved sleep patterns.