To assess the incidence of endometrial polyps during postmenopausal replacement therapy with tibolone, using an appropriate control group.
A total of 485 postmenopausal women were included in this open, prospective, comparative study for a duration of 36 months. Of this group, 249 women received 2.5 mg/day of tibolone and 244 women served as controls, receiving continuous-combined estrogen-progestogen therapy (HT). Transvaginal ultrasound, hysteroscopy, and directed biopsies were performed before treatment was initiated and at the end of the study.
Two hundred twenty-one of the women receiving tibolone and 203 receiving continuous-combined HT completed the study. Endometrial polyps were detected in 74 women (33.4%) from the tibolone group and in 22 women (10.8%) from the HT group (P < 0.01). The vaginal bleeding rate did not differ between the groups. The frequency of atrophic polyps was significantly higher in the tibolone group (P < 0.01). No difference was found in the size of the polyps.
Tibolone increases by threefold the risk for endometrial polyps.