Melatonin, a hormone created in the pineal gland, is responsible for regulating sleep cycles, and plays other minor roles in bodily functions such as immunity and temperature. There are documented correlations between melatonin and menstruation, but the exact effect of melatonin on menstruation is still being investigated. Women with normal menstrual cycles show no significant change in melatonin through the cycle, but melatonin levels vary noticeably in women with menstrual problems.
For women with PMS, melatonin levels may be unusually high or low during the two weeks before starting menstruation. If melatonin levels are low, taking daily melatonin supplements while symptoms are present may alleviate PMS. Taking melatonin and progesterone together has been shown to eliminate PMS in affected women. If melatonin levels are high, bright light therapy may help lower melatonin levels and alleviate symptoms.
There is a positive correlation between low melatonin levels and the onset of female puberty, including the start of menses. Early onset of puberty and menses also is linked to lower than average melatonin production. According to a British study by Dr. Aric Sigman, girls who watch more television tend to start puberty earlier because exposure to the bright lights of television lower melatonin levels.
Secondary amenorrhea is the absence of menstrual periods for six months or longer in women who have passed puberty but not yet entered perimenopause. It may be caused by low body weight, abnormal hormone production, obesity or stress. It is common for women with secondary amenorrhea to have high melatonin levels.
Melatonin naturally decreases as women age, and post-menopausal women usually have low melatonin levels. During the perimenopausal phase, the transition from regular menstruation to menopause, hormones such as estrogen and melatonin fluctuate unpredictably. Melatonin levels are often high during perimenopause.
The function of melatonin, including the effect of melatonin on menstruation, is not yet thoroughly understood. When a woman has high melatonin levels, her estrogen tends to be low, and when she has low melatonin levels, her estrogen tends to be higher. Melatonin may have estrogen-reducing properties, and melatonin treatments for PMS and perimenopause may work by affecting the natural estrogen levels in the body.