Thyroid peroxidase

From Wikipedia, the free encyclopedia

thyroid peroxidase
Identifiers
Symbol	TPO
HUGO	12015
Entrez	7173
OMIM	606765
RefSeq	NM_175722
UniProt	P07202
Other data
EC number	1.11.1.8
Locus	Chr. 2 pter-p24

Thyroid peroxidase or Thyroperoxidase (TPO) is an enzyme mainly expressed in the thyroid that liberates iodine for addition onto tyrosine residues on thyroglobulin for the production of thyroxine (T4) or triiodothyronine (T3) (thyroid hormones).

Inorganic iodine enters the body primarily as iodide, I-. After entering the thyroid follicle via pendrin, thyroid peroxidase oxidizes iodine to atomic iodine (I) or iodinium (I+). The "organification of iodine," the incorporation of iodine to thyroglobulin for the production of thyroid hormone is inseparable from oxidation and is catalyzed by TPO.

[edit] Stimulation and inhibition

TPO is stimulated by TSH, which upregulates gene expression. It is inhibited by the thioamide drugs, such as propylthiouracil.

[edit] Clinical significance

It is a frequent epitope of autoantibodies in autoimmune thyroid disease so the antibody titer can be used to assess disease activity in patients who have developed such antibodies.