Objective: Serum levels of inhibin A, inhibin B, FSH, and LH were measured in healthy volunteers before and during oral or vaginal estroprogestinic administration. In addition, the effect on endometrial thickness and on follicular growth pattern were also assessed by vaginal ultrasound.
Design: Prospective study.
Setting: University of Siena.
Patient(s): Seventeen healthy fertile women.
Intervention(s): This open-label study was performed in 10 healthy volunteers, who were assigned to vaginal ethinylestradiol (15 microg) and etonogestrel (120 microg), one ring to be used for one cycle, after stratification for the ovulation day in a pretreatment cycle. A similar study on seven women assigned to oral ethinylestradiol (20 microg) and levonorgestrel (100 microg) was considered, to compare the effects of the two different routes of administration. Blood samples were collected the cycle before (days 8-10) and during (days 8-10) vaginal ring insertion and serum inhibin B, inhibin A, FSH, and LH levels were measured by ELISA. Concomitantly, transvaginal ultrasound was performed in all subjects for endometrial and follicular growth assessment.
Main outcome measure(s): Inhibin A, inhibin B, FSH, and LH levels.
Result(s): Vaginal administration induced a significant decrease of serum inhibin A, inhibin B, FSH, and LH. No significant changes in inhibin B and FSH secretion were observed during oral contraceptive (OC) administration, whereas LH and inhibin A levels significantly decreased. Endometrial thickness and ovarian volume decreased significantly during vaginal ring insertion, but not after OC administration.
Conclusion(s): The present findings showed that treatment with vaginal estroprogestinic decreases serum inhibin A and inhibin B levels, the follicular diameter, and endometrial thickness, showing a rapid and significant effect with the vaginal route.