Human chorionic gonadotropin reduces aromatizable androgens and aromatase activity in women stimulated by clomiphene citrate and human menopausal gonadotropin.

Periovulatory steroidal dynamics in women undergoing ovulation induction with clomiphene citrate and human menopausal gonadotropin were studied in 31 women with tubal blockage. Serum estradiol levels were significantly reduced 36 hours after human chorionic gonadotropin administration (from 1792 +/- 162 to 926 +/- 132 pg/ml, p less than 0.001). Peripheral levels of testosterone and androstenedione did not change during this periovulatory time. Progesterone and 17 alpha-hydroxyprogesterone, as anticipated, significantly increased with an early rise noted within the first 8 hours of human chorionic gonadotropin administration (p less than 0.001). A significant reduction of the ratios of the steroidal pairs 17 alpha-hydroxyprogesterone-progesterone (17 alpha-hydroxylase) and androstenedione-17 alpha-hydroxyprogesterone (17,20-desmolase) was observed after human chorionic gonadotropin injection (p less than 0.001). Aromatase activity appeared to be inhibited because of a significant reduction in the estradiol/testosterone ratio 34 to 36 hours after human chorionic gonadotropin administration. Thus human chorionic gonadotropin, which triggers ovulation in women treated by clomiphene citrate-human menopausal gonadotropin, appears to partially reduce aromatizable substrate as well as inhibit aromatase activity.