melatonin

IPA: mɛɫʌtˈoʊnɪn

A hormone, related to serotonin, that is secreted by the pineal gland, and stimulates colour change in the skin of reptiles, and is involved in the sleep/wake and reproductive cycles in mammals.
Any material similar in its chemistry and effect to the natural hormone.

Examples of "melatonin" in Sentences

In some parts of Europe, melatonin is available by prescription only.
For the record, melatonin is a hormone, and it's not a regulated drug under the FDA.
This article on sleep and melatonin is also available at Dr. Breus's official blog, The Insomnia Blog.
Now, you probably also know the word melatonin because in supplement form it’s often used as a sleep aid, and for good reason.
It's taken from cows once a week at the break of dawn, as they discharge a lot of a stress-relieving hormone called melatonin during the night.
The agency found evidence that melatonin is effective in treating people who have delayed sleep syndrome, who chronically tend to fall asleep well after midnight.
Many supplement companies and health food stores will claim that melatonin is a natural sleeping aid or nightcap because it "naturally" helps regulate sleep-wake cycles.
Doctors also worry that because melatonin is sold as a supplement, its manufacturing is not as stringently regulated by the Food and Drug Administration as if it were a prescription drug.