Bisphenols as Environmental Triggers of Thyroid Dysfunction: Clues and Evidence

Abstract

Bisphenols (BPs), and especially bisphenol A (BPA), are known endocrine disruptors (EDCs), capable of interfering with estrogen and androgen activities, as well as being suspected of other health outcomes. Given the crucial role of thyroid hormones and the increasing incidence of thyroid carcinoma in the last few decades, this review analyzes the effects of BPS on the thyroid, considering original research in vitro, in vivo, and in humans published from January 2000 to October 2019. Both in vitro and in vivo studies reported the ability of BPs to disrupt thyroid function through multiple mechanisms. The antagonism with thyroid receptors (TRs), which affects TR-mediated transcriptional activity, the direct action of BPs on gene expression at the thyroid and the pituitary level, the competitive binding with thyroid transport proteins, and the induction of toxicity in several cell lines are likely the main mechanisms leading to thyroid dysfunction. In humans, results are more contradictory, though some evidence suggests the potential of BPs in increasing the risk of thyroid nodules. A standardized methodology in toxicological studies and prospective epidemiological studies with individual exposure assessments are warranted to evaluate the pathophysiology resulting in the damage and to establish the temporal relationship between markers of exposure and long-term effects.

Bisphenol A and Type 2 Diabetes Mellitus: A Review of Epidemiologic, Functional, and Early Life Factors

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“…Among many correlated effects and comorbidities associated with coronavirus disease 2019 (COVID-19), those concerning the thyroid gland are also attracting increasing attention. This is not surprising as the thyroid hormones (THs) play a fundamental role in the regulation of multiple processes—development, growth, metabolism and energy supply—as well as in controlling the development of the nervous system during the early stages of life [ 1 ].…”

New Insights into Mechanisms of Endocrine-Disrupting Chemicals in Thyroid Diseases: The Epigenetic Way

“…Bisphenol A (BPA) was associated with increased risk of thyroid nodules (TNs) in Chinese women [52], in accordance with experimental research on animals that strengthened an involvement of this toxicant in thyroid cancer [3]. Additionally, BPA substitutes and halogenated derivatives of BPA do not emerge as safer alternatives to BPA in term of TH disruption and may alter thyroid function at different levels in several cell lines, while in humans some evidence suggested the potential of bisphenols in increasing the risk of TNs [53]. A higher risk of thyroid carcinomas was particularly observed in different volcanic areas of the world, such as Hawaii, Iceland, French Polynesia, New Caledonia, and Sicily in Italy [54,55].…”