melatonin

[mel-uh-toh-nin]

noun Physiology.

a hormone secreted by the pineal gland in inverse proportion to the amount of light received by the retina, important in the regulation of biorhythms: in amphibians, it causes a lightening of the skin.

Origin of melatonin

1955–60; < Greek mélā(s) black + tone + -in²

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for melatonin

Contemporary Examples of melatonin

This helps us regulate our cortisol and melatonin levels for a proper wake and sleep cycle.
Change Your Sense: Biohacking for Beginners
Ari Meisel
March 18, 2014
One more thing, take it in the morning otherwise it can disrupt your sleep since vitamin D and melatonin are inversely related.
These Are The 15 Supplements to Keep In Your Medicine Cabinet
Ari Meisel
December 28, 2013
Worse, disruption of melatonin can contribute to obesity and cardiovascular disease as well.
These 3 Apps Will Help You Sleep Better, Feel Great, and Eat Well
Dave Asprey
December 18, 2013
A dose of melatonin in the morning resets your body clock later while a dose in the afternoon resets it earlier.
The White House Mystery Drug
Barbara Kantrowitz
March 4, 2010

British Dictionary definitions for melatonin

melatonin

noun

the hormone-like secretion of the pineal gland, causing skin colour changes in some animals and thought to be involved in reproductive function

Word Origin for melatonin

C20: probably from mela (nocyte) + (sero) tonin

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for melatonin

1958, from Greek melas "black, dark" (see melanin) + ending from serotonin. So called because its secretion is inhibited by sunlight.

Medicine definitions for melatonin

melatonin

[mĕl′ə-tō′nĭn]

n.

A hormone derived from serotonin and produced by the pineal gland that stimulates color change in the epidermis of amphibians and reptiles and that is believed to influence estrus in mammals.

Science definitions for melatonin

melatonin

[mĕl′ə-tō′nĭn]

A hormone produced in the pineal gland that plays a role in regulating biological rhythms, including sleep and reproductive cycles. In many animals, melatonin also regulates the physiological effects that occur in response to seasonal changes, such as the growth of a winter coat of fur. Chemical formula: C13H16N2O2.

A Closer Look: Melatonin, a natural hormone manufactured by the pineal gland in the brain, communicates information about light to different parts of the body. It helps regulate biological rhythms and plays an important role in the reproductive cycles of many animals. In humans it is best known for helping to regulate the body's circadian sleep-wake cycle. Melatonin production is affected by light exposure to the eyes; melatonin levels rise during the night and fall during the day, becoming almost undetectable. Though it does not actually induce sleep, melatonin can have sleep-promoting effects. Experiments have shown that at high doses melatonin lowers body temperature, decreases motor activity, and increases fatigue. Melatonin production starts falling after puberty, and it can virtually disappear in the elderly, a phenomenon which could help to explain why sleep disturbances are more prevalent among older adults. Marketed as a dietary supplement and touted as a cure-all for insomnia, jet lag, and even cancer and aging, the overall effects of melatonin on human health are still largely unknown.