[Melatonin and circadian rhythm].

Melatonin is produced by the pineal gland mainly at night, with a peak around 3.00 a.m. under normal conditions.

• Melatonin production is regulated by light exposure, which either suppresses or entrains its secretion.
• The suprachiasmatic nuclei generate the cycle of melatonin secretion in response to day/night changes.
• Melatonin plays a key role in synchronizing biological cycles, including temperature and sleep/wake patterns.
• Exogenous melatonin can affect endogenous secretion according to a phase response curve.
• Melatonin may be used to address disorders related to biological rhythms, such as jet lag and insomnia.

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