A comparative study of an estradiol-releasing vaginal ring versus tibolone in postmenopausal women: a transvaginal color Doppler study

Abstract Objective: To evaluate endometrial blood flow characteristics in response to estrogen replacement therapy (ERT) and tibolone in postmenopausal women and to correlate the resistance index (RI) with plasma estradiol levels. Materials and methods: Transvaginal color Doppler ultrasound examinations were performed in 72 asymptomatic, postmenopausal women who demonstrated endometrial thickness ≤ 5 mm. Thirty-six women receiving tibolone and 36 patients receiving ERT by a vaginal ring comprised the study groups. Results: All postmenopausal women treated with tibolone or ERT showed continuous forward end-diastolic flow. The lowest RI was obtained in women with the vaginal ring inserted. The plasma concentrations of estradiol were found to be significantly higher in the vaginal ring group than those of tibolone. Conclusions: The data observed suggest that ERT and tibolone modify normal postmenopausal endometrial perfusion. Tibolone had a weaker estrogenic effect on endometrial blood flow resistance, and vaginal ring treatment enhanced endometrial blood perfusion through vasodilatation.