Melatonin is a circadian rhythm regulator. Our circadian rhythm regulates the wake and sleep cycles, and every cell and organ in our body is affected by it, he said. Melatonin works to keep the circadian rhythm in sync.
Because it is extremely light sensitive, melatonin will react to exposure to morning light when signaled to our brain to reverse its release of melatonin. Morning light simultaneously signals the brain to release cortisol, our wakefulness hormone. Cortisol wakes us up and should be at its peak in the morning. Melatonin and cortisol are of opposite interest; when melatonin is high, cortisol should be low, and vice versa. When one of these is destabilized, our sleep quality is also affected.
