noun[mass noun] Biochemistry
A hormone secreted by the pineal gland which inhibits melanin formation and is thought to be concerned with regulating the reproductive cycle.
- The pineal gland hormone, melatonin, is one of the endproducts regulated by the circadian system.
- Delaying sleep on weekends delays the nightly secretion of melatonin, the sleep hormone.
- Research has found the pineal hormone melatonin is low in migraine patients.
1950s: from Greek melas 'black' + serotonin.
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