Effects of Environmental Chemicals on the Course of Autoimmune Thyroiditis

Abstract

Introduction. The relevance of the research is attributed to the increased incidence of autoimmune thyroiditis in children, especially those dwelling in contaminated areas. Our objective was to study effects of environmental exposures to industrial chemicals on the course of autoimmune thyroiditis. Materials and methods. In order to establish the relationship between specific features of the course of autoimmune thyroiditis and adverse environmental exposures, we conducted a comparative study of incidence rates of thyroid diseases including thyroiditis, cytotoxicity testing, thyroid status assessment, antioxidant activity assays, and thyroid ultrasound. The observation group consisted of 98 children living the area with the developed metallurgical industry while the comparison group included 23 children living in a recreation area. The groups were matched by age and socio-economic characteristics. Results. We established that thyroiditis incidence rates in the industrially polluted area were almost thrice as high as those in the relatively clean area. The observation group was characterized by smoothed sexual differentiation, earlier development of the autoimmune thyroiditis, higher (up to 1.6 times) frequency of typical diffuse structural changes, and increased thyroid gland. Blood levels of metals having a direct cytotoxic effect on the thyroid gland were 2.0 to 6.7 times higher than normal in the cases compared to their matched controls. The correlation and regression analysis established contribution of chemicals to the increased incidence of autoimmune thyroiditis in children (zinc), antibodies to thyroid gland tissue (lead), thyroid-stimulating hormone (nickel), and decreased resistive indices (lead). Conclusion. High blood levels of lead, nickel and zinc were among the factors having an adverse effect on the course of AIT and thyroid function.