Environmental pollutants and the thyroid

• Published in: Baillière's best practice & research. Clinical endocrinology & metabolism Vol. 23; no. 6; pp. 801 - 813
• Main Authors: Pearce, Elizabeth N., Dr, Braverman, Lewis E., Dr
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.12.2009
• Subjects: Animals; Benzhydryl Compounds; Dioxins - pharmacology; endocrine disruptors; Endocrinology & Metabolism; Environmental Exposure; Environmental Pollutants - pharmacology; Female; Fetus - drug effects; Halogenated Diphenyl Ethers - pharmacology; Humans; Hydrocarbons, Chlorinated - pharmacology; Iodide Peroxidase - antagonists & inhibitors; Isoflavones - pharmacology; Lead - toxicity; Liver - drug effects; Nitrates - pharmacology; organochlorine compounds; perchlorate; Perchlorates - pharmacology; Phenols - pharmacology; Polychlorinated Biphenyls - pharmacology; Pregnancy; Styrenes - pharmacology; Symporters - antagonists & inhibitors; Thiocyanates - pharmacology; thyroid; Thyroid Gland - drug effects; Thyroxine - blood; Triclosan - pharmacology; thyroid; endocrine disruptors; organochlorine compounds; perchlorate
• ISSN: 1521-690X; 1878-1594
• DOI: 10.1016/j.beem.2009.06.003

Common environmental exposures may affect thyroid function in humans. Foetuses and infants are most vulnerable to these effects because they need thyroid hormone for normal neurodevelopment. Perchlorate, thiocyanate and nitrate are all competitive inhibitors of the sodium/iodine symporter (NIS) in pharmacologic doses, but their effects on human thyroid function at environmental exposure levels remain unclear. Many compounds, including polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs), bisphenol-A (BPA) and triclosan, may have direct actions on the thyroid hormone receptor, but these effects are complex and are not yet well understood. Isoflavones inhibit thyroperoxidase (TPO) activity, and, therefore, may cause goitre and hypothyroidism if ingested at high levels, particularly in iodine-deficient individuals. Organochlorine pesticides and dioxins may decrease serum T4 half-life by activating hepatic enzymes. Additional studies are needed to further elucidate the risk posed by these and other potentially thyroid-disrupting compounds.