Melatonin is an endocrine hormone that is principally produced and released into the cerebrospinal fluid surrounding our brain by the pineal gland located in the back part of the head and from there into the blood. The levels of melatonin fluctuate according to the activity of the endogenous biological clock that resides in the brain suprachiasmatic nuclei (SCN) and are diminished by bright light exposure (highest during darkness and sleep, and lowest during the day and in bright sunlight). It is proposed that melatonin acts as a time of day (circadian night period) and season (short day photoperiod) cue. Melatonin has been identified as a sleep-anticipating signal in humans and as an important physiological regulator of the sleep-wake cycle2 3.
The hormone melatonin plays a pivotal role in regulating the body’s natural circadian rhythms1. The hormone’s level increases just before onset of sleep, remains in high concentrations throughout the night and falls to almost zero during the day.