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Melatonin - Effective Use and Safety

Melatonin is a hormone produced by the pineal gland in the brain, melatonin also occurs naturally in some foods. It therefore may be sold as a dietary supplement in the United States under

Timekeeping Hormone

Secreted only in the dark, melatonin provides a time-of-day cue to diurnal and nocturnal species. For some animals and birds, it also provides a time-of-year signal for migration, hibernation, and estrus cycles. Melatonin's secretion is one of hundreds of circadian, or approximately 24-hour, rhythms in bodily functions controlled by the suprachiasmatic nuclei (SCN) of the hypothalamus, which comprise the body's master clock. Melatonin receptors have been found in the SCN, which is itself entrained by daylight signals received.

Daylight intensity light-roughly 5 times brighter than ordinary indoor light-suppressed melatonin secretion.

Young adults typically secrete about 5 micrograms to 25 micrograms of melatonin per day. In most people, secretion declines dramatically with age, a fact some researchers suggest accounts for the higher prevalence of meletonin.

Jet Lag and Sleep Loss

The most appropriate applications for melatonin are for problems calling for regulation of the sleep-wake.

Melatonin also may prove helpful to some persons who are totally blind, that is, who lack all light perception. Without daylight signals to anchor their body rhythms to a 24-hour light and dark cycle.

Study Results

Studies of melatonin's effect on sleep have had inconsistent results, a fact variously attributed to timing, dosage, method of delivery, pharmacological profile, pharmacokinetics, interaction with daylight.

Other Adverse Effects

Similar qualms about the general use of melatonin were voiced.