Plasma profile of pituitary gonadotropins and ovarian steroids in women during 17 α-acetoxy- 11 β -methyl-19-nor-progesterone administration

Abstract

The effècts of 17α -acetoxy-11 β -methyl-19-nor-progesterone (SC-21009), a synthetic, active progestin on pituitary and ovarian function, were studied in eleven healthy normally ovulating women. SC-21009 was administered orally at three different doses during a complete menstrual cycle. Four subjects received 40 μg daily; 3 subjects received 200 μg daily and 4 others received 1000 μg daily. Pituitary gonadotropic function was assessed by the daily measurement of radioimmunoassayable levels of plasma LH and FSH. Ovarian steroidogenetic function was evaluated by determining the daily plasma levels of estradiol and estrone, and the levels of progesterone on appropriate days. In addition, the urinary excretion of pregnanediol was also determined. Since we have established the normal hormone profile of these women throughout the menstrual cycle prior to the study, it was possible to compare the data with those obtained during SC-21009 administration. The results obtained demonstrate that the lower dose of SC-21009 (40 μg) significantly increased the plasma LH levels (p < 0.001) through the follicular phase. A concomitant and slight, although not significant, increase in plasma FSH levels was observed. No significative changes at mid-cycle nor during luteal phase were noted. In contrast, higher doses of the synthetic progestin did not induce significative changes on the plasma gonadotropin profile. Estrogens and progesterone levels during SC-21009 at the three doses employed were similar to that observed in the control cycle. These data are interpreted as demonstrating LH-FSH positive feed-back mechanisms at follicular phase during low-dose SC-21009 therapy and a lack of ovulation inhibitory activity of this progesterone derivative.