Thyroid Microsomal (Peroxidase) Antibodies, TPO

Immunology

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Description

Thyroid peroxidase ( TPO ), originally described as thyroid microsomal antigen is present on the surface of thyroid follicular cells and the target for cell mediated cytotoxicity. TPO has been characterized as an integral membrane hemoprotein ( MW 100 kDa ) that catalyzes the iodination of thyroglobulin ( TG ), as well as the coupling of two dityrosine residues in the TG molecule to form thyroxine. TPO antibodies are used to aid in the diagnosis of autoimmune thyroid disease. They are seen in autoimmune hyperthyroidism ( Grave's disease ) and are found in most cases of Hashimoto's disease [1]. TPO antibodies are associated with post-partum thyroiditis. The presence of TPO antibodies in early pregnancy predicts a 30 - 50% chance of postpartum thyroiditis developing [3]. TPO antibodies are not uncommon in apparently healthy individuals but can also precede the development of thyroid dysfunction [2,3]. Patients with subclinical hypothyroidism who are TPO antibody positive are more likely to have a higher TSH and more likely to develop overt hypothyroidism [3]. Autoimmune thyroid diseases are associated with many other autoimmune diseases such as pernicious anaemia, Sjogren's syndrome and coeliac disease. [1] TPO antibodies have also been associated with breast cancer, polycystic ovarian syndrome and increased risk of miscarriage. [1] TPO antibody status should be checked prior to commencing amiodarone and then monitored every six months afterwards. [3]

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Indications

Thyroid disorders. To evaluate the risk of post-partum or neonatal thyroid dysfunction.

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Sample Type

2mL Serum ( Gel 5mL Yellow tube ). Requests from outside Sheffield: Transport at ambient temperature via Royal Mail or Courier.

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Reference Range

Negative <34 IU/mL.Reference range manufacturer derived and verified in house.

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Turnaround Time

Within 5 days

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Testing Frequency

Daily

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References

Sinclair D. Analytical aspects of thyroid antibodies estimation. Autoimmunity. 2008. 41( 1 ):46-54.UK Guidelines for the Use of Thyroid Function Tests. 2006. Sinclair D. Clinical and laboratory aspects of thyroid autoantibodies. Ann Clin Biochem. 2006. 43( 3 ):173-183.Ruf J, Carayon P. Structural and functional aspects of thyroid peroxidase. Arch Biochem Biophys. 2006. 445( 2 ):269-277.Prummel MF, Wiersinga WM. Thyroid peroxidase autoantibodies in euthyroid subjects. Best practice and research clinical endocrinology and metabolism. 2005. 19( 1 ):1-15. [Ref 2]

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See Also

Thyroglobulin antibodies, Anti-Thyroglobulin antibodies

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