Effects of tibolone on the endometrium

To investigate the effects of 24 months of tibolone treatment on the endometrium in postmenopausal women.

An open, prospective, multicenter study with a treatment duration of 24 months.

One hundred and fifty healthy postmenopausal women.

Women were treated with one tablet of tibolone (2.5 mg Org OD14) daily. Endometrial biopsies were taken at baseline, 12 months (n = 112) and 24 months (n = 62) to investigate endometrial histology by means of light microscopy.

No stimulation of atrophic endometrium was observed in 98.2% and 91.9% of the analyzed women after 12 and 24 months, respectively. A change from an atrophic endometrial pattern to a weakly proliferative pattern was seen in 1.8% (95% confidence interval (CI) 0.22-6.45) and 6.5% (95% CI 1.20-7.51) of the women after 12 and 24 months, respectively. In one woman, the endometrial pattern after 24 months was classified as simple hyperplasia (1.6%; 95% CI 0.01-3.20). The low incidence of proliferation and/or hyperplasia corresponds to that seen in other clinical trials in which women have been treated with placebo. Vaginal bleeding and/or spotting was reported by 18 women (12%), all showing an atrophic endometrium at all assessments, except for one woman with a proliferative endometrium at 24 months.

In the majority of women (92%), the endometrium remained atrophic during 24 months of tibolone treatment.