Effects of Prenatal Phthalate Exposure on Thyroid Hormone Concentrations Beginning at The Embryonic Stage

Hui Gao,Yuanyuan Xu,Jie Sheng,Fangbiao Tao,Wanke Wu,Puyu Su,Huihui Bao,Peng Zhu,Zhongxiu Jin,Jiahu Hao

doi:10.1038/s41598-017-13672-x

Abstract

Limited studies have consistently shown an association of phthalates exposure with thyroid hormones (THs) in pregnant women. However, it remains unknown on which specific phthalates can affect THs and whether any effects could differ by gestational age. In the present study, we investigated associations between serum concentrations of phthalate monoesters [monoethyl phthalate (MEP), mono-(n + iso)-butyl phthalate (MBP) and mono(2-ethylhexyl) phthalate (MEHP)] and THs [thyroid-stimulating hormone (TSH), total thyroxine (TT4) and free thyroxine (FT4)] in Chinese pregnant women. 1,397 women were recruited from the China-Anhui Birth Cohort. Maternal serum samples were collected and used to measure phthalate metabolites and THs. Covariate-adjusted linear regression analyses showed that natural log (Ln)-transferred concentrations of MBP and LnMEHP were negatively associated with TT4 (β = −0.277 and –0.461, respectively; p < 0.001). Stratification analyses by gestational weeks showed significant associations of LnMBP and LnMEHP with TT4 in gestational weeks 5 to 8, 9 to 12, and 13 to 20. Our findings suggest an association of serum phthalates with lower TT4. The influence of MBP and MEHP on TT4 concentrations throughout the early pregnancy may begin from the embryonic stage (gestational weeks 5 to 8).

Highlights

To date, a few studies have reported the potential association of phthalate exposure with thyroid function in pregnant women[13,16,25,26,27,28]
Pearson correlation and ANOVA tests showed that maternal age, pre-pregnancy body mass index (BMI), gestational age, residence and passive smoking were associated with at least one type of thyroid hormones (THs)
The result suggested that Chinese women during gestational weeks 5 to 20 were widely exposed to low concentration of DEP, DBP, and DEHP

Summary

Introduction

A few studies have reported the potential association of phthalate exposure with thyroid function in pregnant women[13,16,25,26,27,28]. Our previous study[25] showed negative associations of urinary monobenzyl phthalate (MBzP), mono(2-ethylhexyl) phthalate (MEHP) and mono(2-ethyl-5-hydroxylhexyl) phthalate (MEHHP) with serum TT4 and FT4, whereas positive associations of MEHP and MEHHP with thyroid stimulating hormone (TSH). A repeated measures analysis (median 10, 18, 26, and 35 weeks of gestation)[27] revealed that MEHP and mono-3-carboxypropyl phthalate (MCPP) were positively related to TT4 and FT4, respectively, whereas MEHP, mono-iso-butyl phthalate (MiBP) and MCPP were negatively associated to TSH. These findings suggested that the direction of the associations of THs phthalates with THs phthalates varied during pregnancy[27]. On the basis of the China-Anhui Birth Cohort (C-ABC), the objective of this pilot study was to investigate the cross-sectional association between prenatal serum concentrations of phthalate monoesters and maternal THs concentrations

Methods

Results

Conclusion