The effect of iodine administration on the development of thyroid autoimmunity in patients with nontoxic goiter

Objective: Previous studies, mostly performed in iodine-deficient areas, ha ve suggested that the administration of iodine to patients with endemic goi ter may be associated with the development of thyroid autoantibodies (ThAbs ); however, this has not been a consistent finding. In this study, we evalu ated the effect of iodine on thyroid function and on the development of ind ices of autoimmunity (ThAbs and lymphocytic infiltration) in an iodine repl ete area. Methods: Iodized oil (1 mL) was administered intramuscularly to 4 0 euthyroid patients with nontoxic goiter, adequate iodine intake, and abse nt or normal levels of ThAbs. Blood and urinary samples were taken at time 0, 3, 6, and 12 months after iodine administration. Thyroid volume was eval uated and fine-needle aspiration (FNA) was performed at 0, 6, and 12 months . Results: Seven patients developed abnormal levels of ThAbs at some time b etween 3 and 12 months after iodine administration (p = 0.017). Mean anti-t hyroglobulin (Tg) antibody levels increased at 6 months without reaching ab normal levels, but did not reach statistical significance (p = 0.062). Lymp hocytic infiltration was detected in FNA smears in 10 cases before and in 2 7 cases after treatment (p = 0.0003). Triiodothyronine (T-3) decreased at 1 2 months of follow-up, while thyroxine (T-4) and thyrotropin (TSH) levels d id not change significantly. A decrease in the mean levels of thyroglobulin as well as a small reduction in goiter size was observed at 6 and 12 month s. Conclusion: The administration of iodized oil to patients with small non toxic goiter in an iodine-replete area was accompanied by the development o f abnormal levels of ThAbs in some cases and by an increase in thyroid lymp hocytic infiltration.