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

Bright and blue light (both of which are often found in overhead lighting) can inhibit melatonin production and keep us awake longer. —Halee Miller, Better Homes & Gardens, 25 June 2024

And more children have been hospitalized for accidental melatonin overdoses. —Cara Lynn Shultz, Peoplemag, 18 June 2024

Giving melatonin to young children The poll also found 1 in 5 parents often or sometimes give their child melatonin before bedtime, which came as a surprise given the younger age range of 1 to 6 years old, Clark said. —Taylor Nicioli, CNN, 17 June 2024

Conversely, evenings with more light may delay your body's production of the hormone melatonin, which promotes sleep. —Janet Loehrke, USA TODAY, 10 Mar. 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