Melatonin is a hormone that the body produces in the pineal gland during the dark hours of the 24-hour period. Its levels in the serum during the day are low and that is why it is also called the "hormone of darkness". For this reason, those who work evening hours do not produce enough of it, as well as the elderly.    It is involved in the induction of sleep, reducing the time it takes someone to fall asleep and also in regulating the 24-hour rhythm of the human body (biological clock), relieving the symptoms of jet lag.