Abnormal bleeding in postmenopausal hormone users—What do we know today?

Whilst use of estrogen-containing hormone therapy (HT) has declined in recent years, it is still used by a significant minority of women and remains the most effective way of treating menopausal vasomotor symptoms and vaginal dryness. Unscheduled vaginal bleeding and spotting is a common unwanted effect of combined HT. This abnormal bleeding is inconvenient and commonly leads to invasive tests to exclude underlying pelvic pathology. The mechanisms underlying unscheduled bleeding with HT are poorly understood and there are no evidence-based treatment options. Relatively few studies have investigated how combined hormone therapy induces changes in the endometrium which may predispose to increased bleeding. The available evidence suggests that combined HT induces changes in endometrial blood vessels and stroma which may increase vascular fragility. An improved understanding of how combined HT changes the endometrium to induce bleeding may lead to targeted therapies to effectively prevent or resolve bleeding in postmenopausal women. This will improve the acceptability of combined HT and have personal benefits for postmenopausal women and financial benefits for healthcare providers. This review will discuss current evidence and potential mechanisms underlying unscheduled bleeding with combined HT.