melatonin

noun

mel·​a·​to·​nin ˌme-lə-ˈtō-nən 

: 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

Examples of melatonin in a Sentence

Recent Examples on the Web

The goal is to limit stimulation and stress and avoid unnecessary exposure to the blue light of a screen, which prevents the brain from naturally producing melatonin. —Marie Bladt, Vogue, 10 Oct. 2024

The men were all feeling sleep-deprived this week, so Gary and Charles L. stocked up on some sleep aids — melatonin, ear plugs, etc. — at the drugstore. —Kristen Baldwin, EW.com, 3 Oct. 2024

Actions to Take to Reset Circadian Rhythm Get Light Exposure Upon Waking Your brain produces melatonin to help regulate your circadian rhythm. —Sanja Jelic, Verywell Health, 3 Oct. 2024

As a bonus, this retinol serum alternative also contains melatonin, an ingredient Dr. Robinson says provides overnight hydration and reinforces the skin's natural moisture barrier. —Deanna Pai, Allure, 2 Aug. 2024

Word History

Etymology

mela-, extracted from Greek melan-, mélās "black, dark" + -tonin (in serotonin); so named because the hormone can lighten skin color in animals by reversing the effect of melanocyte-stimulating hormones — more at melano-

Note: The word was probably introduced in the first published description of the hormone's isolation: Aaron B. Lerner, et al., "Isolation of melatonin, the pineal gland factor that lightens melanocytes," Journal of the American Chemical Society, vol. 80, no. 10 (May 20, 1958), p. 2587.

First Known Use

1958, in the meaning defined above

Kids Definition

melatonin

noun

mel·​a·​to·​nin ˌmel-ə-ˈtō-nən 

: a hormone that is secreted by the pineal gland especially in response to darkness and has been linked to the regulation of bodily functions or activities (as sleep) that occur in approximately 24 hour cycles

Medical Definition

melatonin

noun

mel·​a·​to·​nin ˌmel-ə-ˈtō-nən 

: 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