High Prevalence of Thyroid Dysfunction and Autoimmune Thyroiditis in Adolescents after Elimination of Iodine Deficiency in the Eastern Black Sea Region of Turkey

Abstract

In the present study we evaluated the effects of iodine intake on the prevalence of thyroid dysfunction, autoimmunity, and goiter in two regions with different iodine status after two years of iodization in Turkey. In total 1733 adolescent subjects were enrolled into the study (993 from an iodine-sufficient area--the Eastern Black Sea Region (group 1) and 740 from an iodine-deficient area--Middle Anatolia (group 2)). We measured free thyroxine (FT(4)), thyrotropin (TSH), antithyroid peroxidase antibodies (Anti-TPO), antithyroglobulin antibodies (Anti-Tg), and urinary iodine (UI), and examined the thyroid gland by ultrasound. Median urinary iodine excretion was found to be significantly different in group 1 and group 2 (139 micro/l vs 61micro/l, p < 0.001). Hyperthyroidism was more frequent in group 1 (3.6% vs 0.7%; p < 0.001), but the hypothyroidism rate was similar between groups (1.8% vs 1.4 %; p>0.05). The percentage of anti-Tg positive subjects was found to be 17.6% in group 1 and 6.4% in group 2; that of anti-TPO positive subjects was 4.3% in group 1 and 1.5% in group 2. The prevalence of antithyroid antibody (anti-Tg and/or anti-TPO) positivity was significantly higher in group 1 than in group 2 (18.52% vs 6.62%; p < 0.001). Thyroid volumes of the hyperthyroid subjects in both groups were significantly higher than hypo- and euthyroid subjects. In conclusion, iodine supplementation in Turkey has resulted in the elimination of iodine deficiency in the Eastern Black Sea Region, and this has been accompanied by an increase in the prevalence of autoimmune thyroiditis and thyroid dysfunction.

Iodine Excess as an Environmental Risk Factor for Autoimmune Thyroid Disease

“…A large body of epidemiological and clinical data from countries and regions have associated high iodine levels with the development of thyroid autoantibodies and thyroid dysfunctions, including goiter, hypothyroidism, cancers and the morbidity of AIT [35,55,56,57,58,59]. Moreover, multiple animal models, such as the BioBreeding/Worcester (BB/W) rat [60], an obese chicken strain [61,62], the Buffalo rat [63] and the non-obese diabetic (NOD) mouse [64], also suggest that excess iodine is associated with thyroid autoimmunity.…”

Iodine intake and prevalence of thyroid autoimmunity and autoimmune thyroiditis in children and adolescents aged between 1 and 16 years

“…The iodination of thyroglobulin (TG) stimulates the production of antibodies and the proliferation of lymphocytes, which are its pathogenic bases (7). We know that the prevalence of AT increases exponentially decades after supplying iodine in previously deficient areas (8,9) and also that areas with good iodine supply present prevalences between three and five times higher than those found in deficient areas of the same region (10,11).…”

Immunopathogenesis of Thyroiditis

“…HT in adolescents and schoolchildren who have received treatment for iodine deficiency (19,20 ). These epidemiological observations are further supported by a study in which the levels of Tg autoantibodies are increased in patients receiving the iodine-rich, antiarrhythmic drug, amiodarone (15 ).…”