Menorrhagia is most often due to a hormonal imbalance that causes menstrual cycles without ovulation. In a normal cycle, the release of an egg from the ovaries stimulates the body's production of progesterone, the female hormone most responsible for keeping periods regular. When no egg is released, insufficient progesterone can cause heavy menstrual bleeding. Menstrual cycles without ovulation (anovulatory cycles) are most common among two separate age groups:

  • Adolescent girls who have recently started menstruating. Girls are especially prone to anovulatory cycles in the first year and a half after their first menstrual period (menarche).
  • Older women approaching menopause. Women ages 40 to 50 are at increased risk of hormonal changes that lead to anovulatory cycles.
Jun. 25, 2011