Pituitary and gonadal function during the use of progesterone- or progesterone-estradiol-releasing vaginal rings

Six women used polysiloxane vaginal rings impregnated with progesterone, or progesterone and estradiol. Nineteen 3-week treatment cycles were studied. Subjects kept records of bleeding. Plasma progesterone, estradiol, and gonadotropins were measured by radioimmunoassay. The patient acceptance was poor. None of the subjects experienced regular withdrawal bleedings during the treatment-free week. Fifty-three percent of the cycles were ovulatory as judged by plasma progesterone, but the plasma concentration of progesterone was low during the luteal phase. However, no pregnancies were discovered during the study period. Several high estradiol peaks were present during the treatment. Plasma LH fluctuated in the range of the normal menstrual cycle. Some suppression of plasma FSH was observed. The combination of estradiol and progesterone in the rings caused stronger suppression of FSH, but no diminution in the rate of ovulations or in disturbances of bleeding were observed in comparison to rings impregnated only with progesterone. Rings released the same amounts of progesterone in vitro and produced plasma concentrations which varied between 0.4 and 1.9 ng/ml.