Maternal Polybrominated Diphenyl Ether (PBDE) Exposure and Thyroid Hormones in Maternal and Cord Sera: The HOME Study, Cincinnati, USA

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) reduce blood concentrations of thyroid hormones in laboratory animals, but it is unclear whether PBDEs disrupt thyroid hormones in pregnant women or newborn infants. OBJECTIVES: We investigated the relationship between maternal PBDE levels and thyroid hormone concentrations in maternal and cord sera. METHODS: We used data from the Health Outcomes and Measures of the Environment (HOME) Study, a prospective birth cohort of 389 pregnant women in Cincinnati, Ohio, who were enrolled from 2003 through 2006 and delivered singleton infants. Maternal serum PBDE concentrations were measured at enrollment (16 +/- 3 weeks of gestation). Thyroid hormone concentrations were measured in maternal serum at enrollment (n = 187) and in cord serum samples (n = 256). RESULTS: Median maternal serum concentrations of BDEs 28 and 47 were 1.0 and 19.1 ng/g lipid, respectively. A 10-fold increase in BDEs 28 and 47 concentrations was associated with a 0.85-mu g/dL [95% confidence interval (CI): 0.05, 1.64] and 0.82-mu g/dL (95% CI: 0.12, 1.51) increase in maternal total thyroxine concentrations (TT4), respectively. Both congeners were also positively associated with maternal free thyroxine (FT4). We also observed positive associations between BDE-47 and maternal total and free triiodothyronine (TT3 and FT3). A 10-fold increase in BDE-28 was associated with elevated FT3 concentrations (beta = 0.14 pg/mL; 95% CI: 0.02, 0.26). In contrast, maternal PBDE levels were not associated with thyroid hormone concentrations in cord serum. CONCLUSIONS: These findings suggest that maternal PBDE exposure, particularly BDEs 28 and 47, are associated with maternal concentrations of T-4 and T-3 during pregnancy.