Definition of melatonin in English:

Share this entry


Pronunciation: /ˌmɛləˈtəʊnɪn/


[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.
Example sentences
  • 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.

For editors and proofreaders

Line breaks: mela|tonin

Share this entry

What do you find interesting about this word or phrase?

Comments that don't adhere to our Community Guidelines may be moderated or removed.