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. 2025 Sep 2.
doi: 10.1007/s00204-025-04172-3. Online ahead of print.

Associations between environmental phthalates exposure and maternal thyroid hormone levels during pregnancy

Lin Tao  1   2   3 , Shimin Xiong  1   2 , Lulu Dai  1   2   4 , Dengqing Liao  1   2 , Yuan-Zhong Zhou  5   6 , Xubo Shen  7   8
Affiliations

Associations between environmental phthalates exposure and maternal thyroid hormone levels during pregnancy

Lin Tao et al. Arch Toxicol. .

Abstract

Phthalates (PAEs) are well-recognized endocrine-disrupting compounds. Despite their established status as such, the association between maternal exposure to PAEs during pregnancy and the levels of maternal thyroid hormones remains a subject of considerable debate. To shed light on this contentious issue, we conducted an investigation involving 1,156 pregnant women from the Zunyi birth cohort. The aim was to elucidate the relationship between urinary metabolites of PAEs and serum thyroid hormones during the gestational period. In this study, we employed a linear mixed-effects model (LMM) to assess the correlation between PAE metabolites and thyroid hormones. Additionally, restricted cubic spline (RCS) analysis was utilized to explore the dose-response relationship between these PAE metabolites and thyroid hormones. Furthermore, Bayesian kernel machine regression (BKMR) was applied to determine the potential overall effects and to uncover any non-linear relationships that might exist. Our results revealed that several PAE metabolites, namely, monomethyl phthalate (MMP), mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), mono-isobutyl phthalate (MIBP), mono(2-ethyl-5-oxohexyl) phthalate (MOP), and monobenzyl phthalate (MBZP), were associated with correlations involving total thyroxine (TT4), free triiodothyronine (FT3), and free thyroxine (FT4). Subsequently, the restricted cubic spline (RCS) analyses demonstrated a clear dose-response relationship between the PAE metabolites and maternal thyroid hormones, with MEHP, MBZP, MIBP, and MBZP emerging as the major contributors to this relationship. Finally, the BKMR model indicated a non-linear relationship, specifically an inverted U-shaped relationship, between maternal exposure to PAEs during pregnancy and the levels of TT4, FT3, and FT4. Collectively, our findings strongly suggest that exposure to PAEs during pregnancy has a detrimental impact on the secretion of maternal thyroid hormones. To safeguard the health of both the mother and the fetus, it is advisable to minimize exposure to phthalates during pregnancy and to monitor any alterations in thyroid hormone levels closely.

Keywords: Phthalates (PAEs); Pregnant women; Thyroid hormones.

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Conflict of interest statement

Declarations. Conflict of interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Ethical approval: This study was ethically reviewed by the Ethics Committee of Zunyi Medical University (No. [2019] H-005). Consent to participate: All participants agreed to participate in this study and signed the informed consent. Consent for publication: The authors declare that this manuscript does not contain any individual person’s data and material in any form.

References

    1. Barlas N, Göktekin E, Karabulut G (2020) Influence of in utero di-n-hexyl phthalate and di-cyclohexyl phthalate exposure on the endocrine glands and T3, T4, and TSH hormone levels of male and female rats: postnatal outcomes. Toxicol Ind Health 36(6):399–416. https://doi.org/10.1177/0748233720931698 - DOI - PubMed
    1. Boas M, Frederiksen H, Feldt-Rasmussen U et al (2010) Childhood exposure to phthalates: associations with thyroid function, insulin-like growth factor I, and growth. Environ Health Perspect 118(10):1458–1464. https://doi.org/10.1289/ehp.0901331 - DOI - PubMed - PMC
    1. Cathey AL, Watkins DJ, Rosario ZY et al (2020) Polycyclic aromatic hydrocarbon exposure results in altered CRH, reproductive, and thyroid hormone concentrations during human pregnancy. Sci Total Environ 749:141581. https://doi.org/10.1016/j.scitotenv.2020.141581 - DOI - PubMed - PMC
    1. Chen X (2012) Study on phthalate exposure during pregnancy and its effect on reproductive health. Tianjin Medical University, PhD dissertation. (in Chinese).
    1. Choi S, Kim MJ, Park YJ et al (2020) Thyroxine-binding globulin, peripheral deiodinase activity, and thyroid autoantibody status in association of phthalates and phenolic compounds with thyroid hormones in adult population. Environ Int 140:105783. https://doi.org/10.1016/j.envint.2020.105783 - DOI - PubMed

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