Impact on uterine bleeding and endometrial thickness: Tibolone compared with continuous combined estradiol and norethisterone acetate replacement therapy

Objective: To evaluate endometrial thickness and the incidence of uterine b leeding in postmenopausal women using either tibolone 2.5 mg or continuous combined 2 mg estradiol and 1 mg norethisterone acetate (E+NETA) daily as h ormone replacement therapy. Design: We compared diary records of self-reported uterine bleeding and mea surements of endometrial thickness, area, and volume by transvaginal sonogr aphy at baseline and after 1, 3, 6, and 12 months in a 1-year, prospective, randomized, double-blind, single-center trial of 100 postmenopausal women aged 46-69 years. Bleeding frequencies and endometrial thickness were asses sed by Chi-square tests and analysis of covariance, respectively. Results: Self-reported bleeding was significantly less in the tibolone grou p. Bleeding episodes were reported by 27.7% of women in the tibolone group and by 59.2% in the E+NETA group. The mean number of days with bleeding was 5.8 +/- 27.0 in the tibolone group and 35.6 +/- 58.6 in the E+NETA group. Six women in the tibolone group and seven in the E+NETA group discontinued the study; three in the E+NETA group because of bleeding. The mean endometr ial thickness at baseline was 2.56 +/- 0.81 mm in the tibolone group and 2. 58 +/- 1.04 mm in the E+NETA group. After 1 year, the corresponding figures were 3.32 +/- 1.58 mm and 3.07 +/- 1.68 mm. Thus, 86% of women in the tibo lone group and 93% in the E+NETA group had an endometrial thickness of less than 5 mm. Conclusions: Use of tibolone 2.5 mg daily for 1 year was associated with si gnificantly less bleeding and spotting compared with daily continuous combi ned 2 mg estradiol and 1 mg norethisterone acetate in postmenopausal women in the presence of both minimal and nonprogressive increase of endometrial thickness associated with the two regimens. (Menopause 1999;6:299-306. (C) 1999, The North American Menopause Society.).