What are the causes of dysfunctional uterine bleeding during menopause?

Functional uterine bleeding (FUB) during the perimenopausal transition—often referred to as perimenopausal abnormal uterine bleeding (AUB)—arises primarily from hormonal dysregulation rather than structural pathology. As ovarian reserve declines, follicular development becomes increasingly erratic, leading to inconsistent estrogen production and frequent anovulation. Without regular ovulation, there is no corpus luteum formation and thus no progesterone secretion. This results in unopposed estrogen stimulation of the endometrium, causing endometrial hyperplasia and unpredictable, often heavy or prolonged, menstrual bleeding. Additionally, fluctuations in gonadotropin levels—particularly elevated FSH and variable LH—further disrupt hypothalamic–pituitary–ovarian axis feedback mechanisms. While structural causes such as polyps, leiomyomas, or malignancy must always be ruled out—especially in women over 45 with new-onset AUB—the hallmark of functional bleeding is its origin in neuroendocrine dysfunction rather than anatomical abnormality.