The relationship between obesity and race on inhibin B during the menopause transition

Objective: Data are lacking on the effects of obesity and race on inhibin B levels during the menopause transition. The purpose of this study was to determine the relationship among inhibin B levels, body mass index (BMI), and race during the menopause transition. Design: In the Penn Ovarian Aging Study, a prospective cohort study of reproductive aging, 436 women aged 35 to 47 years were followed up with serial hormones, anthropometric measures, and questionnaires for 6 years. Univariate and multivariable analyses were performed comparing mean log transformed inhibin B levels among menopause stages, age groups, BMI categories, races, and smoking groups. Results: In the univariate analyses, mean inhibin B levels were negatively associated with menopause stage, age, and BMI, but not significantly with race or smoking. Interactions of menopause status and BMI were significant (P < 0.001). Premenopausal women with a BMI of 25 or higher had significantly lower inhibin B levels compared with women with a BMI of less than 25 (41.8 pg/mL vs 58.4 pg/mL, P < 0.001), whereas postmenopausal women with a BMI of 30 or higher had significantly higher inhibin B levels compared with the postmenopausal women with a BMI of less than 25 (29.1 pg/mL vs 26.7 pg/mL, P < 0.001). Conclusions: Although BMI is a significant independent predictor of inhibin B levels, the relationship between BMI and inhibin B changes with advancing menopause stage. These data provide additional evidence that obesity influences hormones during the menopause transition.