Background

Evidence on the toxicity of hydroxylated metabolites of polychlorinated biphenyls (OH-PCBs) for thyroid hormones (TH) is limited, and the underlying mechanism remains unknown.

Objectives

We aimed to investigate the effects of environmental prenatal exposure to OH-PCBs and maternal and neonatal TH levels, taking the maternal-fetal TH transfer into account.

Methods

In this prospective birth cohort (the “Hokkaido study”) we included 222 mother-neonate pairs. We measured five OH-PCB isomers in maternal serum samples either during pregnancy or within 5 days of delivery. Thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels were obtained from maternal blood samples at an early gestational stage (median; 11.1 weeks) and from heel prick samples of neonates between 4 and 7 days after birth. Multiple linear regression analysis and structural equation modeling (SEM) were performed to investigate the associations between maternal OH-PCB and maternal and neonatal TH levels.

Results

Median concentration of ∑OH-PCBs was 25.37 pg/g wet weight. The predominant isomer was 4-OH-CB187, followed by 4-OH-CB146+3-OH-CB153. In the fully adjusted linear regression analysis, maternal ∑OH-PCBs was positively associated with maternal FT4, and 4-OH-CB187 was positively associated with both maternal and neonatal FT4 levels. Maternal OH-PCBs showed no significant association with TSH among mothers and neonates. Path analysis indicated the indirect pathway from 4-OH-CB187 exposure to increased neonatal FT4, via maternal THs and neonatal TSH.

Conclusions

These findings suggest that maternal exposure to OH-PCBs during pregnancy may increase both maternal and neonatal FT4 levels. Neonatal FT4 is presumed to be increased by prenatal 4-OH-CB187 indirectly, and this process may be mediated by maternal THs and neonatal TSH.

中文翻译：

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孕妇血清羟化多氯联苯浓度与孕妇和新生儿甲状腺激素的关系：北海道出生队列研究

背景

关于多氯联苯（OH-PCBs）的羟基化代谢产物对甲状腺激素（TH）的毒性的证据有限，其潜在机制尚不清楚。

目标

我们旨在调查产前环境对OH-PCBs的暴露以及母婴TH水平的影响，同时考虑母婴TH转移。

方法

在这个预期的出生队列（“北海道研究”）中，我们包括了222对新生儿。我们在怀孕期间或分娩后5天内测量了孕妇血清样品中的5种OH-PCB异构体。甲状腺刺激激素（TSH）和游离甲状腺素（FT4）的水平是从妊娠早期（中位； 11.1周）的孕妇血液样本以及出生后4至7天的新生儿足跟采血样本中获得的。进行了多元线性回归分析和结构方程模型（SEM），以研究孕妇OH-PCB与孕妇和新生儿TH水平之间的关系。

结果

∑OH-PCBs的中位浓度为25.37 pg / g湿重。主要的异构体是4-OH-CB187，然后是4-OH-CB146 + 3-OH-CB153。在完全调整的线性回归分析中，母亲的∑OH-PCBs与母亲的FT4正相关，而4-OH-CB187与母亲和新生儿的FT4水平正相关。母体OH-PCBs在母亲和新生儿中均与TSH无显着相关性。路径分析表明，通过孕妇TH和新生儿TSH，从4-OH-CB187暴露到增加新生儿FT4的间接途径。

结论

这些发现表明，孕妇在怀孕期间接触OH-PCBs可能会增加孕妇和新生儿的FT4水平。新生儿FT4可能被产前4-OH-CB187间接增加，而这一过程可能是由孕妇TH和新生儿TSH介导的。