INTERFERENCE WITH THE NORMAL FUNCTION OF THE CORPUS LUTEUM BY ORAL ADMINISTRATION OF SYNTHETIC GESTAGENS

Abstract

The peripheral plasma levels of progesterone was used as an indication of the function of the corpus luteum during the administration of four different synthetic gestagens. The gestagens were given orally from the third day after ovulation to normally menstruating women. The day of ovulation was calculated from the changes in the plasma levels of 17β-oestradiol and progesterone. Progesterone was assayed by competitive protein binding and 17β-oestradiol by radioimmunoassay. A pronounced decrease of the plasma levels of progesterone was found during treatment. The lowest total dose with effect was for noretisteron 30 mg, for norgestrel 12 mg for chlormadione acetate 300 mg and for medroxyprogesterone acetate 360 mg. When larger doses of the gestagens were used the progesterone levels decreased to follicular phase levels. A parallel decrease was found for 17β-oestradiol. In all the 32 cycles treated with this or higher doses an evident effect was seen. Injections of human chorionic gonadotrophins (9000 IU) 8 to 10 days after ovulation produced an increase of the progesterone levels despite continuation of the treatment (10 cycles).