Association of urinary bisphenols and triclosan with thyroid function during early pregnancy

Arash Derakhshan,Huan Shu,Robin P Peeters,Andreas Kortenkamp,Christian H Lindh,Barbara Demeneix,Carl-Gustaf Bornehag,Tim I.M Korevaar

doi:10.1016/j.envint.2019.105123

Abstract

BackgroundBisphenols and triclosan are considered as potential thyroid disruptors. While mild alterations in maternal thyroid function can result in adverse pregnancy and child developmental outcomes, there is still uncertainty whether bisphenols or triclosan can interfere with thyroid function during pregnancy. ObjectivesWe aimed to investigate the association of urinary bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF) and triclosan with early pregnancy thyroid function. MethodsThis study was embedded in the Swedish Environmental Longitudinal, Mother and child, Asthma and allergy study (SELMA), a population-based prospective pregnancy cohort. In total, 1996 participants were included in the current study. Maternal urinary concentrations of three bisphenols and triclosan, collected at median (95% range) 10 (6–14) weeks of pregnancy as well as serum concentrations of thyroid stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), total thyroxine (TT4), and total triiodothyronine (TT3) were measured. ResultsHigher BPA levels were associated with lower TT4 concentrations (non-monotonic, P = 0.03), a lower FT4/FT3 ratio (β [SE] -0.02 [0.01], P = 0.03) and a lower TT4/TT3 ratio (β [SE] -0.73 [0.27], P = 0.008). Higher BPF levels were associated with a higher FT3 (β [SE] 0.01 [0.007], P = 0.04). There were no associations between other bisphenols or triclosan and absolute TSH, (F)T4 or (F)T3 concentrations. The association of BPA with thyroid function differed with gestational age. The negative association of BPA with FT4/FT3 and TT4/TT3 ratios was only apparent in early but not late gestation (P for interaction: 0.003, 0.008, respectively). ConclusionThese human data during pregnancy substantiate experimental findings suggesting that BPA could potentially affect thyroid function and deiodinase activities in early gestation.

Highlights

Bisphenols, a group of organic compounds belonging to the class of phenols, are utilized for the production of commonly used plastics such as epoxy resins in food and water containers, thermal receipts, toys and plastic bags
Thyroid function homeostasis is maintained by the hypothalamic-pituitarythyroid axis which is controlled by the negative feedback loop: FT4 binds to thyroid hormone receptors of pituitary and controls the secretion of thyroid stimulating hormone (TSH) and this is reflected by the physiologic log-linear association of TSH and FT4 (Korevaar et al, 2017b; Rothacker et al, 2016); we hypothesized that higher concentrations of bisphenol A (BPA), bisphenol S (BPS) or bisphenol F (BPF), through the explained mechanism, might alter this loglinear association and we investigated this by adding interaction terms of each bisphenol with FT4 to the linear regression models with natural log-transformed TSH as outcome
We investigated the association of urinary BPA, BPS, BPF and triclosan concentrations with thyroid function during pregnancy and we show that a higher exposure to BPA is associated with a lower TT4 and a higher exposure to BPF is associated with a higher FT3

Summary

Introduction

Bisphenols, a group of organic compounds belonging to the class of phenols, are utilized for the production of commonly used plastics such as epoxy resins in food and water containers, thermal receipts, toys and plastic bags. Bisphenols are considered as endocrine disruptors because in vitro and animal studies show that they can interfere with estrogen as well as thyroid hormone action and regulation at multiple levels (Rochester and Bolden, 2015; Boas et al, 2012; Mughal et al, 2018; Ermler et al, 2011). The thyroid hormone disruptive potential of triclosan, another widely used phenolic compound has mainly been studied in animals but requires confirmation in human studies (Weiss et al, 2015; Dann and Hontela, 2011; Paul et al, 2012; Johnson et al, 2016). Objectives: We aimed to investigate the association of urinary bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF) and triclosan with early pregnancy thyroid function. Conclusion: These human data during pregnancy substantiate experimental findings suggesting that BPA could potentially affect thyroid function and deiodinase activities in early gestation

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