Abnormal (or dysfunctional) uterine bleeding is vaginal bleeding that is abnormally frequent, infrequent, heavy, or light. Every year, more than a million women complain of heavy or irregular periods. The terms are relative, but heavy bleeding is classified as a 50% increase in normal flow, or soaking through more than 10 tampons or sanitary pads in a day. Bleeding that lasts longer than a week is also considered to be heavy. Getting a short or light period every two to three weeks instead of one monthly period is considered to be irregular, as is spotting or missing periods altogether.
Half of abnormal uterine bleeding cases occur during the childbearing years. Pregnancy is the most common cause of missed periods. The hormonal changes that occur during the years leading up to menopause (known as perimenopause) are another common cause of skipped periods and menstrual irregularities.
Abnormal uterine bleeding can be broken into two categories: 1) problems that are hormonal in origin; and 2) those that are organic in origin—most commonly fibroid tumors, uterine polyps, or a systemic disease such as cancer or a blood-clotting disorder.
Hormonal imbalances that interfere with ovulation can result in abnormal uterine bleeding. A number of things can interfere with the intricate hormonal balance that affects ovulation and bleeding.
- Pregnancy. In women of childbearing age, pregnancy is the leading cause of skipped periods.
- Perimenopause. The hormonal changes that occur during the years leading up to menopause (the cessation of menstruation) can cause bleeding abnormalities.
- Stress. Stress hormones such as cortisol are known to interfere with ovulation.
- Polycystic ovary syndrome (PCOS). PCOS is a condition in which the ovaries become filled with tiny cysts and enlarge. The problem occurs when the pituitary gland produces too much of a hormone called luteinizing hormone (LH). The hormonal imbalance that results creates an overabundance of uterine lining that makes bleeding irregular.
- Other hormonal causes. Problems that originate in the thyroid gland, pituitary gland, or adrenal glands can disrupt ovulation.
A physical problem in the uterus can cause abnormal bleeding.
- Fibroids. Fibroids are noncancerous growths that invade the wall of the uterus in at least 20% of women over the age of 35. Fibroids may appear singly or in clusters, and be as small as a grape or as big as an orange. They are comprised of muscle and fibrous tissue, and may cause excessive flow during menstruation or bleeding between periods.
- Polyps. Polyps are another type of noncancerous growth that can invade the cervix or uterus. Polyps may be so small that they go unnoticed, or may be big enough to poke into the uterine or pelvic cavity and cause abnormal bleeding.
- Pelvic inflammatory disease (PID). PID is a condition in which the fallopian tubes become inflamed, usually due to a sexually acquired infection. Irregular bleeding is one of the many symptoms of PID.
- Uterine cancer. Uterine cancer is a malignant growth in the uterus. It can occur in the lining of the uterus (endometrium) or in its muscular walls (uterine sarcoma). Endometrial cancer is the most common cancer of the female reproductive system, and almost always strikes postmenopausal women between ages 50 and 70. Any vaginal bleeding that occurs after menopause should be checked out right away.
Abnormal uterine bleeding can be a consequence of another medical problem.
- Blood-clotting disorders. Problems with blood clotting can trigger abnormal uterine bleeding. A coagulation disorder called Von Willebrand’s disease is one culprit, affecting about 1% of the population.
- Eating disorders. Women with very low body fat due to an eating disorder, strict dieting, or excessive exercise frequently can cease to ovulate and menstruate.
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