TPO and hypothyroidism: Hashimoto's thyroiditis (HT), the most frequent form of autoimmune thyroid disease (AITD) is an organ-specific autoimmune disease, characterized by the presence of anti-thyroglobulin (Tg) and anti-thyroid peroxidase (TPO) autoantibodies [3], [4], accompanied by a thyroidal lymphocytic infiltrate which gradually destroys the gland and, ultimately, results in clinical hypothyroidism [5].