Melatonin is a hormone secreted by the pineal gland in the brain regulating other hormones and circadian rhythm in the body. It determines when we sleep and when we awake. Activated by darkness, it remains suppressed during the day. Melatonin levels are age related, with children having high levels which diminish with increasing age leading to disturbed sleep in the aged. It controls the onset of menstruation and menopause in women. Melatonin is known for its antioxidant properties. Melatonin supplements prevent insomnia, improve the quality of sleep and increase morning alertness. It is known to stimulate bone growth, prevent headaches and migraines and reduce depression and anxiety. It reduces sleep disturbances in children with ADHD. Reduced melatonin production leads to an increased risk of cancer.