Thyroid Peroxidase (TPO)

Thyroid peroxidase (TPO) is located on the apical free surface of thyroid epithelial cells. It is directly involved in the oxidation of iodine, the iodination of tyrosine and the coupling of iodinated tyrosine in thyroid cells. TPO is a key enzyme in the synthesis of thyroid hormone. It is highly expressed in normal, hyperplastic and most benign tumor of thyroid tissues, while its expression is significantly reduced in malignant thyroid tumors. Therefore, TPO can be used in the determination of benign and malignant thyroid tumors.