What is Thyroid Peroxidase Antibody?
Thyroid peroxidase antibodies are IgG autoantibodies directed against thyroid peroxidase, the microsomal enzyme that catalyses iodination of thyroglobulin and coupling of iodotyrosines to form thyroxine and tri-iodothyronine. TPOAb are the hallmark of autoimmune thyroid disease, present in more than 90 per cent of patients with Hashimoto thyroiditis and in about 70 per cent of those with Graves disease. Antibody binding does not directly inhibit enzyme activity in vivo; rather, the presence of TPOAb marks lymphocytic infiltration and signals an ongoing autoimmune process that can progressively destroy thyroid follicular cells.