The effects of bisphenol A (BPA) exposure on fat mass and serum leptin concentrations have no impact on bone mineral densities in non-obese premenopausal women.

Objectives: Bisphenol A (BPA) exposure may promote obesity, but its effect on bone mineral density (BMD) has not been reported in humans. We aimed to examine the relationships between BPA exposure, body composition, serum estradiol, leptin, osteocalcin levels and BMDs in healthy premenopausal women.

Design And Methods: In this cross-sectional study, a total of 246 healthy premenopausal women aged 20 years and older with regular menstrual cycles were investigated. Body mass index (BMI), fat mass, fat-free mass and BMDs were measured by DXA. Serum estradiol, leptin, osteocalcin, urinary BPA and NTx levels were also tested.

Results: Urinary BPA levels were positively associated with fat mass (r=0.193, p=0.006) and leptin (r=0.236, p=0.001) but not with fat-free mass after adjusting for age and BMI. BPA was not associated with serum estradiol levels, BMDs, or bone resorption marker NTx and bone formation parameter osteocalcin, either. A multivariate stepwise regression analysis confirmed that serum leptin levels were positively influenced by fat mass (β=0.746, p<0.001) and BPA (β=0.127, p=0.01) but negatively correlated with fat-free mass (β=-0.196, p<0.001). However, the changes of BMDs at the lumbar spine (β=0.298, p<0.001) and femoral neck (β=0.305, p<0.001) were primarily explained by fat-free mass, and were irrelevant of the fat mass, leptin or BPA exposure.

Conclusions: Although BPA exposure is related with increased amount of fat mass and elevated serum leptin levels, it has neutral effect on BMDs in premenopausal women, possibly due to the exclusive role of fat-free mass, which is unrelated to BPA in determining BMDs.