Overview of DUB
Dysfunctional uterine bleeding (DUB) is heavy or irregular menstrual bleeding that is not caused by an underlying anatomical abnormality, such as a fibroid, lesion, or tumor. DUB is the most common type of abnormal uterine bleeding.
Most cases of DUB are associated with anovulatory bleeding (menstruation that occurs without ovulation). Anovulatory bleeding is common in women who have just started menstruating and during the several years preceding menopause. When ovulation does not occur, the level of estrogen and progesterone in the uterus is disturbed, leading to DUB. Anovulation, however, does not always lead to DUB and there are other causes as well. Women with ovulatory cycles (cycles that involve ovulation) may also experience DUB.
Menstrual cycles vary in duration, frequency, and intensity, making abnormalities difficult to determine. Women who have DUB may experience a variety of patterns of bleeding. A woman who bleeds for longer than a week, bleeds more than every 3 weeks or so, bleeds between periods, or bleeds excessively should see a doctor or other health care provider.
DUB is usually painless. Diagnosis involves ruling out other causes of abnormal bleeding. Treatment depends on the intensity and timing of the bleeding, the patient's age, and if she is trying to conceive.
DUB and Anovulation
Anatomy of the Endometrium
The endometrium is the mucous surface that lines the inside of the uterus. It is responsive to hormonal changes and contains several layers of cells that vary in appearance and number throughout the menstrual cycle. During the luteal phase (i.e., 2 weeks prior to menstruation), the endometrium is thick, its epithelial cells and glands are enlarged, and the arteries are swollen. At menstruation, the endometrium sheds. Following menstruation, the endometrium regenerates.
Normal Menstrual Cycle
Menstruation is triggered by a sudden decrease in progesterone and estrogen secretions. The menstrual flow is made up of endometrial cells and tissue, blood, and cervical and vaginal mucus and cells.
After menstruation, the increased secretion of estrogen causes cellular growth and the regeneration of the endometrium. This first half of the menstrual cycle is known as the follicular phase.
Ovulation (the release of an egg from the ovary) normally occurs 2 weeks after the first day of the last menstrual cycle. After ovulation, the secretion of progesterone stops the growth of the endometrium, balancing out the effects of the estrogen. If conception does not occur, progesterone production declines, and menstrual bleeding begins again.
Normally during the menstrual cycle, the production of progesterone in the latter 2 weeks of the cycle balances out the regenerative effects of estrogen, halting further endometrial growth. In anovulation, the level of estrogen does not decline, and progesterone is not secreted to balance out the effects of estrogen.
Endometrial growth does not stop and the endometrial tissue accumulates and thickens, resulting in abnormally heavy bleeding. Also, without progesterone, the endometrium lacks structural support and sloughs off irregularly, causing heavy and/or irregular periods.
Anovulatory periods are common in the 2 or 3 years following menarche (first menstrual period) and during the several years preceding menopause. Up to 80% of menstrual cycles are anovulatory during the first year following menarche. As a woman approaches menopause, she may have 8 to 10 anovulatory periods a year.
Women who take oral contraceptives and those on estrogen replacement therapy may also have anovulatory cycles. Stress and illness can also trigger anovulation.