Etiology

As with any disease, proper determination of the cause is essential for effective treatment. The appropriate methodology for ruling out pathologic causes is beyond the scope of this chapter and can be found in any good text on gynecology (Table 189-1).¹ It is important to be aware of the scope of causes so that one does not just assume that the problem is “dysfunctional uterine bleeding” (DUB)—defined as abnormal uterine bleeding without any demonstrable organic cause. Abnormal bleeding can include menorrhagia, oligomenenorrhea, polymenorrhea, metrorrhagia, menometrorrhagia, and intermenstrual bleeding. Abnormal bleeding is best understood by thinking in categories of abnormalities: hormonal, mechanical, and clotting. Hormonal causes include anovulation and luteal phase defects and stress, exogenous hormones, hypothyroidism, and ovarian cysts. Mechanical causes include uterine polyps, uterine fibroids, endometrial hyperplasia, uterine cancer, intrauterine devices (IUDs), atopic pregnancy, pregnancy, endometriosis, and endometritis. Clotting abnormalities include vitamin K deficiency, drug-induced hemorrhage (heparin, warfarin, aspirin), dysproteinemias, disseminated intravascular coagulation, severe hepatic disease, primary fibrinolysis, and circulating inhibitors of coagulation; not all of these will cause menorrhagia; rather, they give rise to other abnormal bleeding patterns.

TABLE 189-1 Pathologic Causes of Menorrhagia

Data from Federman DD. Ovary. In Dale DC, Federman DD. Scientific American medicine. New York: Scientific American, 1997, 3:III:9-3:III:10.

Abnormalities in Prostaglandin Metabolism

The etiology of functional menorrhagia is currently believed to involve abnormalities in the biochemical processes of the endometrium that control the supply of arachidonic acid for prostaglandin synthesis.^2,3 Menorrhagic endometrium incorporates arachidonic acid into neutral lipids to a much greater extent than normal, whereas its incorporation into phospholipids is lower. The greater arachidonic acid release during menstruation results in the higher production of series 2 prostaglandins, which are thought to be the major factor both in the excessive bleeding seen at menstruation and in the symptoms of dysmenorrhea. The excessive bleeding during the first 3 days appears to be due to the vasodilatory properties of prostaglandins (PGs) E₂ and PGI₂ and the antiaggregating activity of PGI₂, whereas the pain of dysmenorrhea is due to the overproduction of PGF_2a.

Thyroid Abnormalities

The association of overt hypothyroidism or hyperthyroidism with menstrual disturbances is well known. However, even minimal thyroid dysfunction, particularly minimal subclinical insufficiency as determined by testing the thyroid stimulating hormone (TSH), may be responsible for menorrhagia and other menstrual disturbances.⁴ Patients with minimal thyroid insufficiency and menorrhagia have shown dramatic responses to thyroxine.⁴ It has been recommended that patients with long-standing menstrual dysfunction (who have no obvious uterine disease) should be considered for TSH testing. This approach is preferable to the empiric use of thyroid hormone.

Estimating Menstrual Blood Loss

Physicians often believe that they can assess menstrual blood loss by asking the patient to estimate the number of pads or tampons used during each period and the duration of the period. However, studies have demonstrated that there is no correlation between measured blood loss and these assessments.^1,5,6 A woman’s assessment of her blood loss is extremely subjective, as demonstrated by one study finding that 40% of women with a menstrual blood loss exceeding 80 mL considered their periods only moderately heavy or scanty, whereas 14% of those with a measured loss of less than 20 mL judged their periods to be heavy.⁶

Serum ferritin levels may be the best indicator of excessive menstrual blood loss, but their determination may not be practical in terms of immediate need to know. Despite inaccuracies of patient reporting, it is important for the clinician to make an attempt at understanding blood loss. Excessive blood loss should be a concern if a woman is bleeding longer than 7 straight days or more frequently than every 21 days and is changing a pad or tampon every hour for more than half a day. Women who are changing a pad and/or tampon every half hour or even more often require urgent, perhaps emergency attention. Symptoms of light-headedness, dizziness, fainting, or the like are cause for immediate concern. Any amount of bleeding in a postmenopausal woman is considered abnormal.

Psychological Considerations

Stress affects bleeding patterns directly by influencing the hypothalamic/pituitary/ovarian axis. This influence causes anovulation and the subsequent lack of progesterone production. As a result, the endometrium is in an estrogen-dominant state and becomes thickened and plump without the opposing and stabilizing effect of progesterone. This state can then lead to heavy bleeding at the next menstrual cycle. Adolescents account for many of these cases, and the remainder are often perimenopausal women.