Moreover, the prevalence of TPOAb positivity and SCH tended to be higher in the UIC more than or equal to 250 μg/L group compared with the iodine sufficient group, although the difference was non-significant, suggesting that thyroid autoimmunity may damage thyroid function due to increased iodination of thyroglobulin or direct stimulation of immune cells (20). Here, TG is linked to autoimmune thyroid disease.