Biochemical and histological effects of vaginal estriol and estradiol applications on the endometrium, myometrium and vagina of postmenopausal women.

Estrogen and progesterone receptors in the cytosol (ERc, PRc) and estrogen receptors in the nuclear compartment (ERn) were measured in the endometrium, myometrium and vagina of 29 postmenopausal women who underwent hysterectomy. The effects of vaginal estriol (0.5 mg daily) compared to 17 beta-estradiol (0.05 mg daily) therapy on these receptor levels were studied. In addition, the endometrium was examined by light microscopy for estrogenic stimulation. We found biochemical and histological signs of estrogenic stimulation in all three tissues after estradiol as well as estriol therapy. In the vagina the effect of both estrogens on the ERc concentration was different from that in the endometrium and myometrium. The effects of estradiol and estriol on the ERn were comparable in all three tissues. The PRc levels increased significantly in all tissues after estrogen therapy; in the myometrium it was significantly higher after estriol than after estradiol applications. In conclusion, there were no clear differences between vaginal estradiol and estriol medication with regard to the effects on receptor levels in vaginal and uterine tissues. In the histological studies at the light microscopy level similar signs of estrogen stimulation of the endometrium were found following estradiol and estriol medication.