Thyroid Function: a Target for Endocrine Disruptors, Air Pollution, and Radiofrequencies

: Thyroid diseases are progressively increasing, mainly in terms of congenital hypothyroidism, thyroiditis, and childhood thyrotoxicosis. A rapid increase in the incidence of thyroid cancer in children and adolescents has also been observed in the last decades, mirroring the incidence trend observed in adults. This epidemiologic tendency is paralleled by a progressive increment in costs for diagnosis and treatment of thyroid disease. Thyroid diseases depend on both genetic and environmental factors. Growing evidence link both altered thyroid function and thyroid cancer with a number of widely diffused toxic chemicals of anthropogenic origin. These synthetic substances persistently contaminate the environmental matrices (i.e., air, soil, water) and the food chain, and bio-accumulate in humans, starting from in utero life. Environmental toxics as air pollutants, endocrine disruptors, and high-frequency electromagnetic fields can act through common pathways, on common targets, and with trans-generational effects, with combined mechanisms contributing to thyroid damage. As shown by experimental and epidemiologic observation, these mechanisms include modulation of hormone synthesis, transportation and metabolism, direct interference with thyroid hormone receptors, modulation of gene expression, and autoimmunity. Available evidences linking environmental pollutants and thyroid disease, including cancer, should not be underestimated in consideration of the wide, worldwide, and increasing spread of these toxic substances, and of the key role of thyroid hormones in maintaining the systemic metabolic homeostasis and during the development. Thus, primary prevention measures are urgently needed in particular to protect children, the most exposed and vulnerable subjects.