Obese Women Exhibit Reduced Inhibin B and Estradiol SecretionFollowing Pulsatile Intravenous FSH Administration

Introduction: Maternal obesity is an independent risk factor for reduced reproductive fitness. Decreased secretion of FSH in women with obesity is well documented but poorly understood. Furthermore, obese women secrete less protein and steroid hormones from their ovaries. In mice, prior studies have demonstrated that pulsatile release of FSH enhances ovarian function and fertility. Hypothesis: We hypothesize that insufficient FSH pulsatility, as seen in women with obesity, results in inadequate folliculogenesis and reduced ovarian steroid production. We attempt to correct pulsatile FSH secretion in obese women by administering exogenous FSH to compensate for the suppressed circulating ovarian hormones. Our primary outcome is the change in peak inhibin B between pre- and post-treatment. We present results from our interim analysis. Methods: Reproductive aged, regularly menstruating, normal weight (NW) (BMI 18.5-24.9) and obese (OB) (BMI >30) women were recruited for a 26hr study during the early follicular phase. Frequent blood sampling (q10min) for 10h was performed to obtain baseline hormone levels. At 10h, 3 mg of cetrorelix, a gonadotropin hormone antagonist, was given followed by a secondary dose (0.25mg) 6h later. At this time, hourly IV recombinant (r)FSH (30IU) was initiated and frequent blood sampling continued for 10h. LH, FSH, estradiol (E2) were measured by immunoassay (Advia Centaur XP, Siemens). Inhibin B was measured using an ELISA kit (Ansh labs). Differences between groups were modeled by linear regression, adjusted for age and cycle day (continuous). The relationship between change in peak inhibin B and change in peak E2 was estimated in a linear regression. Results: A total of 36 participants (19 NW and 17 OB) were included in our interim analysis. There were no differences in age, cycle day of study, race, and waist/hip ratio. Inhibin B and E2 rises following the intervention were statistically significant within each group. Peak Inhibin B and E2 levels following intervention were lower in obese women compared to normal weight (133.4 vs 202.5 pg/mL and 85.8 vs 126.4 pg/mL, respectively). The difference in pre and post peak inhibin B levels trended lower in the obese group (-40.1 (95%CI: -86.2, 6.1, p=0.087). No difference was seen in maximal E2 response. There was no relationship between inhibin B and E2 response [0.08 (95%CI -0.26, 0.42), p=0.634]. Conclusions: These early results suggest obese women may have a lower response to pulsatile rFSH as compared to normal weight counterparts even with intravenous administration. We speculate this may be due to decreased uptake of rFSH in obese patients or a sign of ovarian dysfunction in obese women. Additional subjects are recruited to detect these differences.