Endometrial morphology after 6 months of continuous treatment with a new gonadotropin-releasing hormone superagonist for contraception.

Light and electron microscopic studies were performed on endometrial curettage specimens from 27 women after 6 months of contraceptive treatment with continuous intranasal gonadotropin hormone-releasing hormone (GnRH) superagonist. The GnRH superagonist nafarelin acetate (D-Nal[2]6-GnRH) was used in single daily doses of 125 or 250 micrograms. Ovulation was inhibited during all but one of the 159 treatment months. No pregnancies occurred. In 6 women with fairly regular bleedings, the endometrium displayed weak to normal proliferation. Twenty women developed oligomenorrhea or amenorrhea, 16 of them had inactive endometrium, 1 had weakly proliferative endometrium, and 3 endometrial biopsies were too sparse for adequate evaluation. One woman reported repeated episodes of heavy uterine bleedings. The endometrial biopsy from this woman showed weak proliferation. No signs of endometrial hyperplasia were observed. Generally, the electron microscopy showed signs of low metabolic activity and weak protein synthesis. Thus, long-term continuous treatment with nafarelin acetate for inhibition of ovulation does not appear to have untoward effects on the endometrium.