Melatonin is a hormone that is secreted by the pineal gland. The pineal gland is believed to regulate the body’s biological clock. Melatonin is found in abundance early in one’s life, but the levels drop steadily with old age. Although melatonin’s possible benefits are still under debate, some recent studies cite many possible uses of melatonin. It is believed that melatonin boosts the immune system.