Causes

In some cases, the cause of heavy menstrual bleeding is unknown, but a number of conditions may cause menorrhagia. Common causes include:

• Hormone imbalance. In a normal menstrual cycle, a balance between the hormones estrogen and progesterone regulates the buildup of the lining of the uterus (endometrium), which is shed during menstruation. If a hormone imbalance occurs, the endometrium develops in excess and eventually sheds by way of heavy menstrual bleeding.

  A number of conditions can cause hormone imbalances, including polycystic ovary syndrome (PCOS), obesity, insulin resistance and thyroid problems.

• Dysfunction of the ovaries. If your ovaries don't release an egg (ovulate) during a menstrual cycle (anovulation), your body doesn't produce the hormone progesterone, as it would during a normal menstrual cycle. This leads to hormone imbalance and may result in menorrhagia.
• Uterine fibroids. These noncancerous (benign) tumors of the uterus appear during your childbearing years. Uterine fibroids may cause heavier than normal or prolonged menstrual bleeding.
• Polyps. Small, benign growths on the lining of the uterus (uterine polyps) may cause heavy or prolonged menstrual bleeding.
• Adenomyosis. This condition occurs when glands from the endometrium become embedded in the uterine muscle, often causing heavy bleeding and painful periods.
• Intrauterine device (IUD). Menorrhagia is a well-known side effect of using a nonhormonal intrauterine device for birth control. Your doctor will help you plan for alternative management options.
• Pregnancy complications. A single, heavy, late period may be due to a miscarriage. Another cause of heavy bleeding during pregnancy includes an unusual location of the placenta, such as a low-lying placenta or placenta previa.
• Cancer. Uterine cancer and cervical cancer can cause excessive menstrual bleeding, especially if you are postmenopausal or have had an abnormal Pap test in the past.
• Inherited bleeding disorders. Some bleeding disorders — such as von Willebrand's disease, a condition in which an important blood-clotting factor is deficient or impaired — can cause abnormal menstrual bleeding.
• Medications. Certain medications, including anti-inflammatory medications, hormonal medications such as estrogen and progestins, and anticoagulants such as warfarin (Coumadin, Jantoven) or enoxaparin (Lovenox), can contribute to heavy or prolonged menstrual bleeding.
• Other medical conditions. A number of other medical conditions, including liver or kidney disease, may be associated with menorrhagia.