TPO (thyroid peroxidase) gene encodes a membrane-bound glycoprotein th at functions in the iodination of tyrosine residues in thyroglobulin and the formation of phenoxy-ester between pairs of iodinated tyrosines to generate the thyroid hormones, thyroxine and triiodothyronine (T3 and T4). Defects in this gene can cause congenital hypothyroidism, congenital goitre and thyroid hormone organification defect IIA.
