Overview
Dysfunctional uterine bleeding (DUB) refers to irregular or heavy menstrual bleeding that occurs in the absence of an anatomical abnormality such as a tumor, fibroid, or other lesion. The majority of cases of DUB are associated with anovulatory bleeding, which is menstruation that occurs in the absence of ovulation. DUB is the most common type of abnormal uterine bleeding, and occurs most often in young women who have just begun menstruating and in the few years preceding menopause. In the absence of ovulation (when an egg is released from an ovary), estrogen and progesterone levels are disturbed which can then initiate bleeding. Anovualtion however is not the only cause of DUB as women who ovulate may also have DUB. Roughly 90% of DUB is caused by anovulation, while 10% occurs with ovulatory cycles.
The frequency of DUB appears to affect 5% of females with menstrual cycles.1 DUB does not necessarily differentiate between race, however African American women typically have higher levels of estrogen that can predispose them to more episodes of abnormal vaginal bleeding. DUB is most common at the early and late periods of a woman’s reproductive years. In adolescent women, hormonal control by the hypothalamus and pituitary gland may be depressed due to the normally low estrogen production in this age group while in perimenopausal women DUB can be a sign of early ovarian failure.2 DUB can cause significant problems for women, because of the large amount of blood that can be lost at menstruation that at times can be severe enough to cause hemorrhagic shock.
Diagnosis
Menstrual cycles can vary in duration, frequency, and intensity that can sometimes make abnormalities difficult to determine. A woman with DUB may have a variety of bleeding patterns; a woman that bleeds in between periods, excessively at periods, for longer than a week, and bleeds more than every 3 weeks should consult with a physician. Diagnosis involves ruling out other causes of abnormal bleeding, and the treatment will depend on the intensity and timing of the bleeding in the cycle, and the woman’s age and if she is trying to conceive.
In an anovulatory cycle, progesterone that is normally secreted from the corpus luteum (a specialized glandular structure on the ovary) does not occur, and the effects of estrogen (the buildup of the endometrium) are left unopposed.3 This results in abnormally heavy bleeding as the endometrium has been allowed to grow thicker than it would have had progesterone been present.
During ovulatory DUB, prolonged secretion of progesterone leads to irregularly timed shedding of the endometrium, which can appear as spotting rather than a concise menstrual flow. Progesterone can also cause estrogen to be enzymatically converted to a weaker form (estrone), thereby further weakening the effects of estrogen in the body.
A diagnosis of dysfunctional uterine bleeding is typically made by excluding other conditions. One of the most common causes of abnormal uterine bleeding is pregnancy or pregnancy-related problems such as ectopic pregnancy (when a fertilized egg implants someplace other than the uterus) or miscarriage. Abnormalities in the menses may also be the first sign of hypo- or hyperthyroidism, and when irregular and heavy, bleeding of this type may be attributed to kidney or liver failure. It is important for the clinician to rule out any specific disease process prior to making the diagnosis of DUB; it is estimated that 20% of adolescents with DUB have problems with blood clotting.
Causes
Dysfunctional uterine bleeding is typically the result of three different mechanisms:
1. Estrogen breakthrough bleeding: The most common cause of DUB, this occurs when ovulation does not happen, resulting in a state of high estrogen and low progesterone.4 When ovulation does not occur, the corpus luteum (which produces progesterone) fails to form. This allows the uterus to be continually exposed to estrogen until the levels are so high that feedback from the brain (in the form of decreased follicle stimulating hormone) causes estrogen levels to decline somewhat. Eventually, parts of the endometrium slough while other parts are built up by the continuous presence of estrogen. This results in periodic, irregular spotting. When the overall level of estrogen is high, a long period of time may pass without a menstrual flow that is then followed by profuse bleeding with excessive blood losses. If the overall estrogen levels are lower, women may experience prolonged, intermittent spotting that is generally light in flow.
2. Progesterone breakthrough bleeding: This occurs when an excessive ratio of progesterone to estrogen exerts its influence on the endometrium. Typically this situation occurs in women taking only progesterone-containing birth control pills.5 When low amounts of estrogen are present in comparison to progesterone, intermittent bleeding of variable duration occurs, similar to low-dose estrogen breakthrough bleeding. These patients usually respond to lower progesterone containing contraceptive, or one that contains some estrogen.
3. Estrogen withdrawal bleeding: This can occur when the production of estrogen by the ovaries is interrupted in the absence of progesterone. This can also occur in a postmenopausal woman who has been given supplemental estrogen, and the treatment is discontinued; some bleeding will occur when the estrogen no longer affects the uterus.
Based on these three primary mechanisms, a physician will need to conduct further tests that may involve measuring hormone levels and the application (and sometimes withdrawal) of different forms of estrogen or progesterone in order to correct the dysfunctional bleeding. Each patient is dealt with in a different way, due to the various factors that may be contributing to that woman’s irregular bleeding. DUB, once diagnosed, is typically a hormone-based problem in which the timing and or levels of female hormones are imbalanced. Again, there are various causes for these imbalances as well, and the physician and patient together may be able to determine the reasoning for this. The most important part of diagnosing DUB is that no other, more serious condition is present-DUB is not a truly dangerous condition except in the event of excessive blood loss, and can be relatively well treated once the nature of the imbalance is identified and corrected.
- Wren BG. Dysfunctional uterine bleeding. Aust Fam Physician. 1998 May; 27(5): 371-7.
- Bayer SR, DeCherney AH. Clinical manifestations and treatment of dysfunctional uterine bleeding. JAMA 1993; 269:1823-8.
- ohnson CA. Making sense of dysfunctional uterine bleeding. Am Fam Physician 1991; 44:149-57
- Fayez JA. Dysfunctional uterine bleeding. Am Fam Physician 1982; 25:109-15.
- Wall DM, Roos MP. Update on combination oral contraceptives. Am Fam Physician 1990; 42:1037-48.