Urinary bisphenol A and thyroid function by BMI in the Korean National Environmental Health Survey (KoNEHS) 2012-2014

Bisphenol A (BPA) is one of the largest amounts of chemicals in daily life and source of polycarbonate plastics, epoxy resins, medical equipment, plastic consumer products. Recent studies reported that the effects of BPA on human health in the thyroid hormone. Therefore, this study aimed to indicate the association between urinary BPA concentration and thyroid function in total triiodothyronine (T3), thyroxine (T4), thyroidal stimulating hormone (TSH) and stratified the population by body mass index (BMI). This study was performed on 6478 adults aged 19 years and older based on the Second Korean National Environmental Health Survey (KoNEHS, 2012-2014). We measured BPA in urine and total T3, T4 and TSH in serum from the 2nd KoNEHS study. The multiple regression analysis was performed to assess the association of urinary BPA concentrations with thyroid hormone after BMI stratification. Urinary BPA associated with thyroid hormone. Especially, BPA is related to T3 (-0.627) in all group, and T4 (-0.060, -0.098) in all group and the group of BMI 25.0kg/m2 or more negatively. When stratified by BPA, T3 and T4 were significantly decreased with the high BPA exposure compared with the low BPA exposure for BMI more than 25.0kg/m2 (adjusted β = -3.402, 95% CI: 4.942, -1.862, adjusted β = -0.209, 95% CI: 0.328, -0.090). However, no obvious associations were found between BPA concentration and TSH. The results of urinary BPA decrease with T3 and T4 levels increase in the higher BMI group is a new finding which does not exist in recent studies of Korea.