TPO

TPO or Thyroid Peroxidase is an enzyme expressed mainly in the thyroid where it plays a key role in the production of thyroid hormones. A thyroid is a butterfly-shaped gland located in the neck, and it produces hormones that regulate the body's metabolic rate, heart and digestive function, muscle control, brain development, and bone maintenance.

TPO is a membrane-bound glycoprotein which, like all peroxidases, contains heme. Its main function is to catalyze the biosynthesis of the thyroid hormones thyroxine (T4) and triiodothyronine (T3).

Function

TPO is involved in the iodination of tyrosyl residues in thyroglobulin (Tg) to form monoiodotyrosine (MIT) and diiodotyrosine (DIT). It also catalyzes the coupling of these iodotyrosyl residues to form T4 and T3, which are then released into the bloodstream.

Clinical Significance

TPO is the major autoantigen of the thyroid. Autoantibodies to TPO (TPOAb) are found in nearly all patients with Hashimoto's thyroiditis and in the majority of patients with Graves' disease, both of which are autoimmune diseases of the thyroid.

TPOAb are also found in other autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, and type 1 diabetes.

See Also

• Thyroid function tests
• Thyroid disease
• Thyroid hormones
• Thyroid-stimulating hormone

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References

External Links

• TPO gene on the US National Library of Medicine website
• TPO on GeneCards

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