TRANSVAGINAL ADMINISTRATION OF PROGESTERONE

Objective: To examine the endometrial effects of three different doses of progesterone administered vaginally. Methods: Forty women 25-41 ye ars old deprived of ovarian function received estradiol (E2) for 28 da ys. From days 15 to 27, a new mucus-like vaginal gel of progesterone w as administered every other day, randomly, dosed at 45 mg (group A, n = 14), 90 mg (group B, n = 13), or 180 mg (group C, rr = 13). Plasma g onadotropins, estrone, E2, and progesterone were measured. An endometr ial biopsy was performed on day 20 (n = 20) or 24 (,n = 20) for endome trial dating and for estrogen and progesterone receptor determinations . Results: Plasma estrogen levels were in the menstrual cycle range, M ean progesterone levels were lower in group A (2.4 +/- 0.2 ng/mL) than in group B (3.6 +/- 0.2 ng/mL) or C (3.4 +/- 0.4 ng/mL) (P < .005). P lasma FSH and LH decreased significantly during progesterone treatment . In all groups, we observed secretory transformation in the glands (d ay 20) and stroma (day 24) and the distribution of estrogen and proges terone receptors seen in normal menstrual cycles. Conclusion: Transvag inal administration of progesterone induced normal secretory transform ation of the endometrium despite low plasma levels, suggesting a direc t transit into the uterus or ''first uterine pass effect.'' (C) 1997 b y The American College of Obstetricians and Gynecologists.