Adequate sleep has long been known to be vital to good health. Melatonin, a hormone produced by the pineal gland during the dark phase of the light/dark cycle, regulates the sleep/wake cycle and the “biological clock”. However, it is now known also to have free radical scavenging and antioxidant properties and a significant role in stimulating the immune system to protect against the growth of abnormal tissues such as breast and prostate cancers. Melatonin is also neuroprotective. Adequate melatonin production during the night, as well as suppression of production during the day by exposure to daylight, form a balance that is vital to optimal health. Circulating melatonin is rapidly and efficiently hydroxylated and conjugated with sulfate in the liver to form its primary metabolite, 6-sulfatoxymelatonin (MT6s), and excreted into urine; it is this metabolite that is measured in the Sleep Balance Profile.

Cortisol, a hormone produced by the adrenal glands in response to stress, is also known for its diurnal variation linked to the sleep/wake cycle. It has the opposite pattern to melatonin production in a healthy individual. While melatonin rises at night to peak during the early hours of the morning, cortisol is at its lowest levels throughout the night. After waking, melatonin production dips with the onset of daylight and cortisol rises and peaks about 30 minutes to 1 hour after rising. Cortisol production falls gradually during the day, while melatonin begins to rise during the evening as daylight diminishes, and the cycle repeats itself. When the cortisol pattern is disrupted, for example as a result of excessive stressors, this can lead to high night cortisol, disrupted sleeping patterns, and exposure to more night time light, which in turn leads to lowered levels of melatonin. Thus, excessive stressors can lead to higher cortisol and indirectly lower melatonin synthesis, preventing melatonin from carrying out its other beneficial and protective functions.