Autoimmune thyroiditis has a higher prevalence in societies that have a higher intake of iodine in their diet, such as the United States and Japan. Also, the rate of lymphocytic infiltration increased in areas where the iodine intake was once low, but increased due to iodine supplementation. “The prevalence of positive serum tests in such areas rises to over 40 percent within 0.5 to 5 years.” [1]