Ultrastructure of endometrium of postmenopausal patients on two modes of hormonal therapy: estrone sulfate with or without MPA.

The response of human postmenopausal endometrium to standard, oral doses of an estrogen alone (estrone sulfate) and to an estrogen plus a progestin (medroxyprogesterone acetate; MPA) was evaluated by scanning electron microscopy and transmission electron microscopy. Endometrial biopsies were obtained over a 4-year period from 12 patients with well-established ovarian failure. Biopsies were taken before the initiation of therapy and during each mode of hormonal treatment. The ability of estrone sulfate alone to stimulate growth of the endometrium was shown during the 1st treatment cycle when the atrophic epithelial cells transformed into tall columnar cells which synthesized and released some secretory products. Unopposed estrogen therapy led to excessive ciliation and breakthrough bleeding. Addition of MPA to the estrone sulfate regimen produced a progestational endometrium. The epithelial cells had ultrastructural features of those in normal postovulatory endometrium, including nucleolar channel systems. MPA elicited deciliation and transformation of ciliated cells into secretory cells. Stromal cells hypertrophied, the vascular endothelium thickened, and bleeding subsided. Estrogen-progestin therapy as tremendously more physiological than unopposed estrogen therapy.