Ultrasound appearance of the uterus in women over 60 years of age on tibolone: is it a SERM?

OBJECTIVES: To evaluate the effects of long-term tibolone on the endometria of asymptomatic women over the age of 60 years. METHODS: An observational study of the ultrasound appearance of the endometria of women aged 60 years or older taking long-term tibolone. Those found to have a double-layer endometrial thickness greater than 4 mm were offered endometrial biopsy. RESULTS: Seventeen asymptomatic patients with a mean age of 61 years (range 60-73 years) and an average duration of tibolone use of 5 years (range 3-12 years) were recruited. Seven patients (41%) showed a thickened endometrium of more than 4 mm. Three of these had an area of translucency in the subendometrial space. Of the ten women with an endometrial thickness of less than 4 mm, four showed the presence of subendometrial fluid. Hysteroscopy was performed in five out of the seven women, as two did not accept further investigations. In all five women, the endometrial cavity was reported as atrophic and the histology showed an inactive basal type. In two of the five cases examined histologically, there were additional changes suggesting endometrial polyp, although the samples were from macroscopically non-polypoid endometrium. DISCUSSION: Endometrial thickness is increased in 41% of elderly women on long-term treatment with tibolone. However, at hysteroscopy, the endometrium was uniformly atrophic. Similar finding have been described in women using selective estrogen receptor modulators and a similar mechanism of action of these drugs on the uterus should be considered.