The causes of abnormal uterine bleeding are most commonly linked to the hormones estrogen and progesterone. While every woman’s cycle is different, generally speaking women have cycles that last between 24 and 34 days, with a period lasting between four and seven days. Changes in hormone levels can cause a woman’s period to be later, earlier or heavier than normal, and dysfunctional bleeding often occurs when the ovaries do not produce an egg.
Menorrhagia, or heavy or prolonged bleeding, can, in addition to hormonal causes, also be caused by pelvic inflammatory disease; uterine fibroids; an abnormal pregnancy such as a miscarriage or ectopic pregnancy; pelvic infection, tumors or polyps; birth control devices, bleeding or platelet disorders; high levels of prostaglandins (chemicals that help control uterine muscle contractions) or endothelins (chemicals that help blood vessels dilate); or liver, kidney or thyroid disease. In some cases, certain types of cancer can also be a factor.