DUB usually results from an imbalance in the hormonal-endometrial relationship whereby estrogen persistently and unopposedly stimulates the endometrium. Sustained high estrogen levels result from polycystic ovary syndrome, obesity, immaturity of the hypothalamic-pituitary-ovarian mechanism (in postpubertal teenagers and perimenopausal females), and anovulation from vigorous exercise, stress, malnutrition, and certain medications.

The endometrium typically shows no pathologic changes; however, in chronic unopposed estrogen stimulation (for example, from a hormone-producing ovarian tumor), the endometrium may exhibit hyperplastic or malignant changes.

Anemia is a complication of DUB. The condition may also have social consequences, affecting work or school performance.

The patient with DUB typically reports episodes of vaginal bleeding between menses (metrorrhagia), heavy or prolonged menses (longer than 8 days [hypermenorrhea]), or a menstrual cycleof less than 18 days (chronic polymenorrhea).