A shift or imbalance in hormone levels is the main cause of light periods. Light periods most commonly affect women who are approaching menopause because at that time in their lives women produce less estrogen, one of the hormones that regulates menstrual periods. Light periods can also occur in girls who have just begun to menstruate. An eating disorder, excessive exercise, or a thyroid condition can also cause a woman to have light periods. Women who use hormonal contraceptives, including oral contraceptives, may also experience lighter periods. Consult Gynecologist for further evaluation...