Causes

Dysmenorrhea

• Contraction-Causing Chemicals. Powerful chemicals known as prostaglandins and arachidonic acid can induce uterine muscle contractions. Prostaglandins also play a large role in the heavy bleeding that causes dysmenorrhea.
• Abnormal Nervous System Response. Some women with primary dysmenorrhea may have autonomic nervous systems that are overly sensitive to menstrual cycle changes. The autonomic nervous system regulates heart rate and blood pressure, and it contains the pain receptors in nerve fibers in the uterus and pelvic area. As a result, women with autonomic nervous system abnormalities may have a more intense response to pain.
• Abnormalities in the Arteries in the Uterus. Impaired blood flow through the arteries in the uterus may cause severe dysmenorrhea for some women.
• Genetic Factors. Genetic factors may play an important role in over half of primary dysmenorrhea cases.
• Endometriosis. Endometriosis is a chronic and often progressive disease that develops when the tissue that lines the uterus (endometrium) grows onto other areas, such as the ovaries, bowels, or bladder. [For more information, see In-Depth Report #74: Endometriosis.]

• Uterine Fibroids. Fibroids are noncancerous growths that grow on the walls of the uterus. They can cause heavy bleeding during menstruation and cramping pain. [For more information, see In-Depth Report #73: Uterine fibroids.]
• Other Causes. Pelvic inflammatory disease, ovarian cysts, and ectopic pregnancy. The intrauterine device (IUD) contraceptive can also cause dysmenorrhea.

Abnormal Uterine Bleeding

Abnormal uterine bleeding may occur as infrequent episodes, excessive flow, prolonged duration of menses, or bleeding between menses.

Dysfunctional Uterine Bleeding (DUB). DUB is a general term for abnormal uterine bleeding. It is usually caused by hormonal problems. DUB usually occurs either when girls begin to menstruate or when women approach menopause, but it can occur at any time during a woman's reproductive life.

• About 90% of DUB events happen when ovulation is not occurring (anovulatory DUB). In such cases, women do not properly develop and release a mature egg. When this happens, the corpus luteum does not form. As a result, estrogen is produced continuously, causing an overgrowth of the uterus lining. The period is delayed in such cases, and when it occurs menstruation can be very heavy and prolonged.
• The other 10% of DUB cases occur in women who are ovulating (ovulatory DUB), but progesterone secretion is prolonged because estrogen levels are low. This causes irregular shedding of the uterine lining and break-through bleeding.

Abnormal uterine bleeding may also be related to other causes unrelated to the natural cycle or ovulation: