melatonin


mel·a·to·nin

noun \ˌme-lə-ˈtō-nən\

Definition of MELATONIN

:  a vertebrate hormone that is derived from serotonin, is secreted by the pineal gland especially in response to darkness, and has been linked to the regulation of circadian rhythms

Origin of MELATONIN

Greek melas black + -tonin (as in serotonin)
First Known Use: 1958

mel·a·to·nin

noun \ˌmel-ə-ˈtō-nən\   (Medical Dictionary)

Medical Definition of MELATONIN

: a vertebrate hormone C13H16N2O2 that is derived from serotonin, is secreted by the pineal gland especially in response to darkness, and has been linked to the regulation of circadian rhythms

melatonin

noun    (Concise Encyclopedia)

Hormone secreted by the pineal gland of most vertebrates. It appears to be important in regulating sleeping cycles; more is produced at night, and test subjects injected with it become sleepy. Melatonin may be involved in seasonal affective disorder. In mammals other than humans, melatonin may act as a cue to breeding and mating in season.

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