Objective To examine the endometrial effects of three different doses of progesterone administered vaginally
Methods Forty women 25–41 years old deprived of ovarian function received estradiol (E2) for 28 days. From days 15 to 27, a new mucus-like vaginal gel of progesterone was administered every other day, randomly, dosed at 45 mg (group A, n = 14), 90 mg (group B, n = 13), or 180 mg (group C, n = 13). Plasma gonadotropins, estrone, E2, and progesterone were measured. An endometrial biopsy was performed on day 20 (n = 20) or 24 (n = 20) for endometrial dating and for estrogen and progesterone receptor determinations.
Results Plasma estrogen levels were in the menstrual cycle range. Mean 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). Plasma FSH and LH decreased significantly during progesterone treatment. In all groups, we observed secretory transformation in the glands (day 20) and stroma (day 24) and the distribution of estrogen and progesterone receptors seen in normal menstrual cycles.
Conclusion Transvaginal administration of progesterone induced normal secretory transformation of the endometrium despite low plasma levels, suggesting a direct transit into the uterus or “first uterine pass effect.”
Address reprint requests to: Renato Fanchin, MD, Department of Obstetrics and Gynecology and Reproductive Endocrinology, Hôpital Antoine Béclère, 157, rue de la Porte de Trivaux, 92141 Clamart, France
© 1997 The American College of Obstetricians and Gynecologists
Transvaginal administration of progesterone leads to normal secretory transformation of the endometrium despite low plasma levels, hence the suggestion of a “first uterine pass effect.”