Melatonin is a hormone secreted by the
pineal gland, a gland about the size of a pea located in the center of the brain.
Production of melatonin by the
pineal gland is inhibited by light and stimulated by darkness. For this reason melatonin has been called
"the hormone of darkness" and its onset each evening is called the
Dim-Light Melatonin Onset (DLMO).
It helps regulate other hormones and maintains the body's
circadian rhythm.
The circadian rhythm is an internal 24-hour “clock” that plays a critical role in when we fall asleep and when we wake up. When it is dark, your body produces more melatonin; when it is light, the production of melatonin drops. Being exposed to bright lights in the evening or too little light during the day can disrupt the body’s normal melatonin cycles. For example, jet lag, shift work, and poor vision can disrupt melatonin cycles.
Melatonin also helps control the timing and release of female reproductive hormones. It helps determine when a woman starts to menstruate, the frequency and duration of menstrual cycles, and when a woman stops menstruating (menopause).
Some Ways Melatonin is Used:
Insomnia
The hormone melatonin is used to treat circadian rhythm sleep disorders and some types of insomnia.
Studies suggest that melatonin supplements may help people with disrupted circadian rhythms (such as people with jet lag or those who work the night shift) and those with low melatonin levels (such as some seniors and people with schizophrenia) to sleep better.
A number of human studies have measured the effects of melatonin supplements on sleep in healthy people. A wide range of doses has been used, often taken by mouth 30 - 60 minutes prior to sleep time. Results have been mixed. Some evidence suggests that melatonin may work best for people over 55 who have insomnia.
One study of 334 people aged 55 and older found that sustained-release melatonin seemed to help people fall asleep faster, sleep better, be more alert in the morning, and improve quality of life in people with primary insomnia.
Studies have found that the use of melatonin can help train the circadian clock to conform to your environmental cycles and has beneficial effects for the treatment of certain forms of insomnia.
Some evidence suggests that melatonin may help promote sleep in children in
ADHD, although it does not seem to improve the behavioral symptoms of
ADHD.
Immune System Booster
Melatonin has strong antioxidant effects. Preliminary evidence suggests that it may help strengthen the immune system. Immune system cells are typically very vulnerable to free radical damage.
Some researchers also believe that melatonin levels may also help slow the aging process. For example, young children have the highest levels of nighttime melatonin. Researchers believe these levels drop as we age.
Menopause
Melatonin supplements may help with sleep problems associated with menopause. However, it does not appear to relieve other symptoms of menopause, such as hot flashes.
Headaches
Several clinical studies indicate that supplementation with melatonin is an effective preventive treatment for migraines and cluster headaches.
Mood Disorders
Melatonin has been shown to be effective in treating one form of depression, seasonal affective disorder,[68] and is being considered for bipolar and other disorders where circadian disturbances are involved.
Cancer
Clinical trials involving a total of 643 cancer patients using melatonin found a reduced incidence of death. Another clinical trial is due to be completed in 2012. It has been shown that women with the brightest bedrooms have an increased risk for breast cancer. Reduced melatonin production has been proposed as a likely factor in the significantly higher cancer rates in night workers.
Several studies suggest that melatonin levels may be associated with breast cancer risk. For example, women with breast cancer tend to have lower levels of melatonin than those without the disease. Laboratory experiments have found that low levels of melatonin stimulate the growth of certain types of breast cancer cells, while adding melatonin to these cells slows their growth. Preliminary evidence also suggests that melatonin may strengthen the effects of some chemotherapy drugs used to treat breast cancer.
Studies show that people with prostate cancer have lower melatonin levels than men without the disease. In test tube studies, melatonin blocks the growth of prostate cancer cells. In one small-scale study, melatonin -- combined with conventional medical treatment -- improved survival rates in 9 out of 14 men with metastatic prostate cancer.
