The role of selective oestrogen receptor modulators in the treatment of endometrial bleeding in women using long-acting progestin contraception

This paper explores the concept that endometrial breakthrough bleeding results from the stimulatory effects of oestrogen in the endometrium. Though 'progestin-only' contraceptive regimens have long been associated with user dissatisfaction because of unpredictable vaginal bleeding, it is likely that the substantial contribution of endogenous ovarian oestradiol during such treatments predisposes the bleeding problems. Oestrogen causes endometrial proliferation, hyperplasia and neoplasia if unopposed. Oestrogen allows production of growth factors supporting angiogenesis which results in an abundance of dilated or fragile endothelial surface blood vessels, predisposing this tissue to bleeding when these vessels lose competence.