Ultrastructural aspects of the postmenopausal endometrium after oral or transdermal estrogen administration

In this report we examined the ultrastructural features of the postmenopausal endometrial cells of women treated with different doses of conjugated equine estrogen (CEE), or transdermal 17beta-estradiol. Eight women with uterine prolapse and at least 5 years of menopause were randomly divided into four groups and treated as follows: (I) no hormonal treatment; (II) 0.625mg/day of CEE orally; (III) 1.25mg/day of CEE orally; (IV) 50microg/day of 17beta-estradiol transdermally. Hormones were administered for 28 days followed by vaginal hysterectomy. Fragments of the endometrium were prepared for transmission electron microscopic analysis. We observed that the postmenopausal endometrium of the untreated group was atrophic with lined superficial epithelial cuboidal cells. The presence of gland and stroma cells with clear cytoplasm containing few organelles and heterochromatin nuclei were also observed. On the contrary, the endometrium of the group that received 0.625mg/day of CEE showed signs of proliferative cells such as the presence of numerous organelles in the cytoplasm and euchromatic nuclei. All of the proliferative effects on the endometrium were more pronounced in the groups that received 1.25mg/day of CEE and 50microg/day of transdermal 17beta-estradiol. We concluded that the ultrastructural proliferative changes of the postmenopausal endometrium induced by 1.25mg/day of CEE were similar to 50microg/day of transdermal 17beta-estradiol.