Levels of hydroxylated polychlorinated biphenyls (OH-PCBs) and thyroid function in pregnant women

Abstract

Background Polychlorinated biphenyls (PCBs) are persistent contaminants. PCBs are metabolized into hydroxylated metabolites (OH-PCBs) now considered possibly more toxic than the parent compounds. Because PCBs may be associated with perturbed thyroid function, we examined the relationship between five OH-PCBs and thyroid function in pregnant women. Aims To examine the relationship between five OH-PCBs and 3 measures of thyroid function in pregnant women. Methods Stored postpartum sera from 442 pregnant women from the Child Health and Development Studies were analyzed for five OH-PCBs (4-OH-CB107, 3-OH-CB153, 4-OH-CB146, 3'-OH-CB138 and 4-OH-CB187) and stored second trimester sera were analyzed for free thyroxine (FT4), thyroid stimulating hormone (TSH) and thyroid peroxidase antibodies (TPOAb). Spearman correlation (r) was used to examine the bivariate associations between each OH-PCB and each measure of thyroid function. Linear regression was used to examine the associations adjusting for potential confounders. Results Median concentrations of 3-OH-CB153, 4-OH-CB146, 3'-OH-CB138were all 0.03 ng/ml. Median levels of 4-OH-PCB107 and 4-OH-CB187 were higher; at 0.08 ng/ml and 0.38 ng/ml, respectively. Mean (+ sd) concentrations of free T4, TSH, and ATPO were 1.26 (+0.21) ng/dl, 1.49 (+1.09) uIU/ml, and 28.9 (+76.6) IU/ml, respectively. Parent-compound and metabolites were correlated at 0.152-0.398. We found positive associations between 4-OH-CB107 and FT4 (estimated regression coefficient b = 0.030, p =.029), and between TSH and both 4-OH-CB187 (b = 0.099, p =.029), and 3-OH-CB153 (b = 0.065, p =.033). Conclusions Levels of OH-PCBs were consistent with reported literature. We found small associations between selected OH-PCBs and FT4 and TSH, suggesting that OH-PCBs are associated with maternal thyroid status. Exposure may result in adverse outcomes in the developing fetus, and emphasize the need for research on long term outcomes associated with PCB exposure and thyroid dysfunction.