Endometrial histology and progesterone levels in women using norethindrone acetate implants for contraception.

Abstract The effect of a single implant-D containing 40 mg of norethindrone acetate was studied on the endometrium of twenty women using this method of contraception for 7–27 months, the endometrial dating is correlated with serum progesterone levels. Ovulation was indicated in 19 of them by serum progesterone being more than 3 ng/ml and presence of secretory endometrium, while in one woman the premenstrual endometrial biopsy showed proliferative endometrium and serum progesterone was 2.1 ng/ml. Dating of endometrium was difficult as there was disparity between glandular, stromal and vascular components. It showed retarded endometrium in 5 and enhanced in 4 suggesting thereby that one of the modus operandi of this implant might be through bringing about minor endometrial changes, while ovulation remains uninhibited.