TPO and Autoimmunity: AITD are the most frequent autoimmune disorders with an estimated prevalence of 7 to 8%14,46,89 and a reported female predominance of 9:1.46 They include 2 main clinical entities: (a) chronic lymphocytic thyroiditis (or Hashimoto thyroiditis), which leads to hypothyroidism and (b) Graves’ disease (or Basedow disease), leading to hyperthyroidism.12,14,89 Hashimoto thyroiditis is characterized by the production of anti-thyroglobulin (anti-Tg) and anti-thyroperoxidase (anti-TPO) autoantibodies, which progressively lead to gland fibrosis and hypothyroidism.