Improving iodine nutritional status and increasing prevalence of autoimmune thyroiditis in children

The objective of this study is to evaluate the link between excess iodine intake as evidenced by increased urinary iodine excretion (UIE) and autoimmune thyroiditis in children and to assess the correlation between UIE and thyroid microsomal antibody (thyroid peroxidase [TPO]) titers in children.

All children with goiter between age group 6 and 12 years, were subjected to blood tests for free thyroxine, thyroid stimulating hormone, and TPO antibody, fine needle aspiration was advised for all children with goiter. Forty-three children with confirmed autoimmune thyroiditis served as cases, and 43 children with euthyroid goiter with workup negative for autoimmune thyroiditis and iodine deficiency were enrolled as controls. UIE was estimated in spot urine sample for both cases and controls. The levels of urinary iodine were compared between cases and controls.

The levels of urinary iodine were significantly higher in children with autoimmune thyroiditis as compared with control. There was a positive correlation between UIE and antimicrosomal antibody titers among cases. Among cases 65% children had subclinical hypothyroidism, 27.9% had overt hypothyroidism and 7% of cases, and 100% of controls had euthyroid functional status. Excessive (≥300 μg/L) UIE was strongly associated with autoimmune thyroiditis. If the UIE level is ≥ 300 μg/L, then there is 17.94 times higher chance of having amiodarone-induced thyrotoxicosis than those who have UIE level < 300 μg/L (P < 0.001).

A possible association between increased iodine intake and autoimmune thyroiditis was found in this study. Excessive iodine intake may trigger thyroid autoimmunity and eventually thyroid hypofunction.