Serum Polybrominated Diphenyl Ether Concentrations And Thyroid Function In Young Children

Abstract

Introduction: Thyroid hormones are essential for neurodevelopment in early childhood. There is evidence that exposure to polybrominated diphenyl ethers (PBDEs) affects thyroid function, but previous studies have been inconsistent, and no studies in children have been conducted in the United States where PBDE levels are particularly high. Methods: Serum levels of six low-brominated PBDE congeners and thyroid hormones were measured in a sample of healthy children (N=81) aged 1-5 years who were under anesthesia for ear tube surgery. Parents of the children completed a questionnaire with details on demographics, behaviors such as smoking and breastfeeding, and family history of thyroid disorders. In multivariate linear regression models, we assessed quartiles and continuous log-transformed PBDE concentrations in relation to markers of thyroid function. PBDEs were expressed on a volume basis, and serum lipids were included as a covariate. Results: Detection frequencies varied by congener. PBDE-47, 99 and 100 were detected in =80% of samples, and were summed (∑PBDE). The median ∑PBDE was 54.04 ng/g lipid or 0.19 ng/mL. PBDEs were positively associated with thyroid-stimulating hormone (TSH) and inversely associated with total thyroxine (T4). Compared with children in the lowest quartile of ∑PBDE exposure, children in higher quartiles had significantly increased TSH (β=0.45, 95% confidence interval (CI): 0.04, 0.85, β=0.46, 95% CI: 0.07, 0.86, and β=0.48, 95% CI: 0.06, 0.90 for the second, third and fourth quartiles, respectively). For an interquartile range increase in ∑PBDE we estimated a 20.9% increase in TSH (95% CI: 3.4, 41.2), and a 0.28 ug/dl decrease in total T4 (95% CI: -0.76, 0.20). Conclusion: Results suggest that exposure to PBDEs during childhood disrupts thyroid hormone function, with a tendency toward hypothyroidism. These results highlight the importance of considering early life exposures in the context of critical windows of development.