TPO

Thyroid peroxidase (TPO) is a transmembrane glycoprotein that mainly exists in the apical membrane of thyroid follicular epithelial cells. TPO is a crucial enzyme in the synthesis of thyroid hormones. It can catalyze the iodination and coupling of tyrosine residues in thyroglobulin (TG), ensuring the normal production of thyroid hormones and indirectly promoting the metabolism and development of the body. Some research found that TPO is widely present in benign diseases such as nodular goiter and thyroid follicular adenoma, but not expressed in thyroid malignant tumors. Therefore, TPO can be used as a differential biomarker for thyroid benign and malignant lesions. However, TPO has low specificity and limited value when used alone, so it is often used in combination with CD56, CK19, TG, Galectin-3, HBME-1, and other antibodies. The specific mechanism of TPO down-regulated expression is still unclear, but some scholars believe that the low expression is associated with tumor metastasis and recurrence, which may be because the abnormal change in TPO can induce the tyrosine metabolism disorder.