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Bisphenol A (BPA), the monomeric component of polycarbonate plastics, reportedly possesses endocrine-disrupting effects. Exposure to low levels of BPA during more vulnerable periods leads to abnormalities related to sexual development in experimental animals. Moreover, recently a few epidemiological studies in Caucasians have demonstrated the association of BPA exposure with type 2 diabetes. Therefore, in the present study we examined the association of BPA exposure and abnormal glucose tolerance in Thais. This is a cross-sectional study of 240 participants aged at least 50 years, randomly selected by computer-generated random numbers within each glucose tolerance status from an oral glucose tolerance study of 661 participants. There were 80 participants in each group of type 2 diabetes, impaired glucose tolerance (IGT) and normal glucose tolerance (NGT). Serum BPA was measured by competitive ELISA. The detection rate of BPA was significantly higher in participants with IGT compared to those with NGT ( p < 0.05), while no difference was found between participants with type 2 diabetes and NGT. When participants with type 2 diabetes were stratified into those with fasting plasma glucose (FPG) under the diabetic threshold (<126 mg/dL) and those over (≥126 mg/dL), it was found that those with FPG under the diabetic threshold had measurable rates of BPA comparable to those with IGT, and rates significantly higher than the NGT group ( p < 0.05), while those with FPG over the diabetic threshold did not have higher rates of measurable BPA compared with the NGT group. In conclusion, BPA exposure is not uncommon in Thais. There is an association between BPA exposure and IGT, but not type 2 diabetes.

Background: Epidemiological studies of the association between bisphenol A (BPA) exposure and diabetes have been inconsistent. The present study determined serum BPA concentrations in the Thai population and their association with hyperglycemia and diabetes., Methods: In all, 2581 serum samples from the Thai National Health Examination Survey (2009) were used to determine BPA levels. Impaired fasting glucose (IFG) was defined as fasting plasma glucose ≥100 and <126 mg/dL. Diabetes was defined as a history of a physician's diagnosis or fasting plasma glucose ≥126 mg/dL. Multinomial logistic regression was used to examine the association of serum BPA with IFG and diabetes., Results: Of 2581 samples tested, BPA was detected in 2135 samples (weighted percentage 78.1%), with a geometric mean concentration of 0.34 ng/mL BPA. Serum BPA levels were significantly higher among those with diabetes or IFG compared with normoglycemic individuals (0.52 and 0.38 vs 0.33 ng/mL, respectively; P < 0.001). After adjusting for potential confounders, compared with the first quartile (≤0.071 ng/mL), the overall adjusted odds ratios (OR) of serum BPA concentration in the third and fourth quartiles (0.319-0.745 and ≥0.746 ng/mL, respectively) for IFG were 1.72 (95% confidence interval [CI] 1.19, 2.49) and 1.23 (95% CI 0.80, 1.89), respectively; for diabetes, the adjusted OR were 1.88 (95% CI 1.18, 2.99) and 1.83 (95% CI 1.12, 2.95), respectively, with a slightly stronger association among men than in women., Conclusions: Serum BPA concentrations were not associated with IFG, but were positively associated with diabetes in the Thai population. Further prospective studies are needed to confirm the relationship., (© 2014 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and Wiley Publishing Asia Pty Ltd.)

Bisphenol A (BPA) is a chemical that is used in a variety of consumer products, and exposure to BPA is widespread among the general population. Recent studies have suggested that BPA may affect the thyroid and related pathways. However, human studies are still limited. The aim of this study was to determine the relationship between BPA exposure and thyroid function. We obtained survey data and blood samples from The Thai National Health Examination Survey IV 2009, a nationally representative cross-sectional survey using a multistage, stratified sampling of the Thai population. A total of 2,340 subjects aged 18-94 years were sampled for the present study. Serum BPA, TSH, FT4, and related covariates were measured. BPA was log-transformed prior to analysis. BPA was detected in 52.8 % of serum samples with a median concentration of 0.33 (range 0-66.91) ng/mL. We excluded subjects who tested positive for thyroid autoantibody and then stratified the remaining subjects by gender; the analysis showed a significantly negative correlation between serum BPA and FT4 levels in males (r = -0.14, P < 0.001). In contrast, no association was observed in females. BPA was not associated with TSH in either gender. This gender-related discrepancy is possibly related to androgen-related differences in the metabolism of BPA. Our preliminary results provide evidence of a negative association between BPA and FT4 levels. Additional detailed studies are needed to investigate the temporal relationship and potential public health implications of such an association.