Comparing multiple measures of body mass as predictors for testosterone and estradiol levels in men

Prior studies have shown that increased body mass in men is associated with decreased levels of testosterone and increased levels of estradiol. These hormone alterations can lead to fertility issues. Body mass can be measured as body mass index (BMI, kg/m2), waist circumference, or waist-to- height ratio. However, limited literature exists on which measure of body mass is the best predictor of hormone levels. Identifying the most accurate measure of obesity and how it alters testosterone and estradiol hormone levels in men can help guide future fertility research and screening.
The National Health and Nutrition Examination Survey data from August 2021 to 2023 from the United States’ Center for Disease Control was utilized for 5,575 nationally representative men aged 18 years and older. Predictor variables include BMI, waist circumference, and waist-to-height ratio.
Outcomes of interest were serum testosterone and estradiol levels. Confounding variables adjusted for include age, race, smoking, alcohol use, physical activity, diabetes, and high cholesterol. Linear regressions were performed between each measure of body mass and both hormones. Regression lines were compared between body mass measures using a one-way ANOVA with post-hoc Tukey tests.
BMI (β1=-11.8, F(11,2114)=33.42, P<0.001, R2 =0.15), waist circumference (β1=-5.1, F(11,2065)=38.29, p<0.001, R2 =0.17), and waist-to-height ratio (β1=-912.1, F(11,2063)=38.21, p<0.001,
R2 =0.17) were all associated with decreased testosterone levels. Waist-to-height ratio was found to be a better predictor of testosterone levels than BMI (p<0.001) but not waist circumference (p=0.07). BMI (β1=0.21, F(11,2103)=5.17, P<0.001, R2=0.03), waist circumference (β1=0.06, F(11,2054)=3.74,
p<0.001, R2 =0.02), and waist-to-height ratio (β1=10.6, F(11,2052)=3.73, p<0.001, R2 =0.02) were all associated with increased estradiol levels. No measure of body mass was more predictive of estradiol levels (F(2)=0.39, p=0.67).
This study builds upon the established association between obesity and sex hormone alterations, specifically decreased testosterone and increased estradiol levels. Waist-to-height ratio is more comparable to waist circumference in predicting hormone levels, with both measures more predictive than BMI is predicting testosterone levels, suggesting either waist circumference or waist-to- height ratio is the preferential measure of obesity screening. Characterizing specific obesity measures and their associations with reproductive hormones provides insight into potential pathways linking obesity and infertility.