TMELATONIN IS A NATURAL hormone made by your body's pineal (pih-knee-uhl) gland. The pineal gland lies at the base of the brain. And when the sun goes down, and darkness comes, the pineal gland "goes to work." As melatonin production rises, you begin to feel less alert. Body temperature starts to fall as well. Sleep seems more inviting. Then melatonin levels drop quickly with the dawning of a new day. Levels are so low during the day that scientists often have difficulty detecting melatonin then.

Melatonin levels go hand in hand with the light-dark cycle, not just for people, but for plants and animals that keep alert during the day. Melatonin production is also related to age. Children manufacture more melatonin than the elderly do. But melatonin production begins to drop at puberty.

Melatonin or 5-methoxy-N-acetyltryptamine is an important hormone that plays a role in regurating the neuroendocrine system. It plays an important role in the reguration of the circadian sleep-wake cycle. It also controls essential functions such as metabolism, sex drive, reproduction, appetite, balance, muscular coordination and immune system in fighting off diseases triggered by bacteria, viruses, chemical pollutants and excessive free radical activity. It is normally released during the night in response to environmental changes in light levels by the peneal gland which is a tiny gland burried deep in the brain behind the eyes of mammals. The pineal itself is controlled by a paired cluster of nerve cells located just above the optic chiasm in the hypothalamus. These cells are known as the suprachiasmatic nuclei (SCN) and they contain the circadian pacemaker. Each night the SCN send impulses, via a series of neurons in the hypothalamus and spinal cord, up to the pineal gland to stimulate melatonin secretion. The timing mechanism in the SCN itself is controlled by sunlight that enters the retina and reaches the SCN via the retinohypothalamic pathway. The amount of melatonin circulating in the blood has been shown to rise and fall during a day. The 24-hour cycle of melatonin production in Human is shown in figure 1 below;