Thyroid peroxidase (TPO)

The TPO gene provides instructions for making an enzyme called thyroid peroxidase. This enzyme plays a central role in the function of the thyroid gland, a butterfly-shaped tissue in the lower neck. Thyroid peroxidase assists the chemical reaction that adds iodine to a protein called thyroglobulin, a critical step in generating thyroid hormones. Thyroid hormones play an important role in regulating growth, brain development, and the rate of chemical reactions in the body (metabolism).

What is the official name of the TPO gene?

The official name of this gene is “thyroid peroxidase.”

TPO is the gene's official symbol. The TPO gene is also known by other names, listed below.

What other names do people use for the TPO gene or gene products?

• MSA
• PERT_HUMAN
• thyroid microsomal antigen
• thyroperoxidase
• TPX

What is the normal function of the TPO gene?

To function properly, thyroid peroxidase must be located in the cell membrane of certain thyroid cells, called follicular cells. Thyroid peroxidase has several different versions (isoforms), which vary by size and location within the cell. Some versions are inactive because they are not located in the cell membrane.

How are changes in the TPO gene related to health conditions?

• Congenital hypothyroidism - caused by mutations in the TPO gene
  

Researchers have identified more than 30 TPO mutations that delete, add, or change DNA building blocks (base pairs) in the TPO gene. Some mutations lead to an abnormally small thyroid peroxidase enzyme that breaks apart before it can be inserted into the cell membrane. Other mutations change the enzyme's 3-dimensional shape, preventing it from functioning properly within the cell membrane. Without functional thyroid peroxidase, iodine taken up by the thyroid gland is not added to thyroglobulin. As a result, the production of thyroid hormones is absent or reduced, leading to the features of congenital hypothyroidism. In most affected individuals, the thyroid gland is enlarged (goiter) in an attempt to compensate for reduced hormone production.

• Autoimmune disorders - associated with the TPO gene
  

A major cause of thyroid disease is autoimmunity, in which the body's immune response turns against itself. The autoimmune response is triggered by a combination of genetic and environmental factors and involves the production of large Y-shaped proteins called antibodies or immunoglobulins. Instead of attacking foreign substances such as toxins or proteins from bacteria and viruses, these antibodies inappropriately attack thyroid proteins. Antibodies that attack the body's own proteins are called autoantibodies. The presence of autoantibodies to thyroid peroxidase is an indication of autoimmune thyroid disease.

The two most common thyroid autoimmune diseases are Graves disease and Hashimoto thyroiditis. Abnormal levels of thyroid hormones and an enlarged thyroid gland (goiter) are features of these disorders. Autoantibodies to thyroid peroxidase are present in about 75 percent of people with Graves disease and 90 percent of those with Hashimoto thyroiditis.

Where is the TPO gene located?

Cytogenetic Location: 2p25

Molecular Location on chromosome 2: base pairs 1,396,241 to 1,525,501

The TPO gene is located on the short (p) arm of chromosome 2 at position 25.

More precisely, the TPO gene is located from base pair 1,396,241 to base pair 1,525,501 on chromosome 2.

What glossary definitions help with understanding TPO?

antibody ; antigens ; autoantibody ; autoimmune ; autoimmune disease  ; autoimmunity ; bacteria ; base pair ; cell ; cell membrane ; congenital ; DNA ; enzyme ; gene ; goiter ; Graves Disease ; hormone ; hypothyroidism ; immune response ; immunoglobulin ; iodine ; isoforms ; metabolism ; mutation ; protein ; thyroglobulin ; thyroid ; thyroid hormones ; tissue ; toxin ; virus

External Links

See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.

Where can I find additional information about TPO?

You and your healthcare professional may find the following resources about TPO helpful.

• MedlinePlus - Health information

• Encyclopedia: Autoimmune disorders (http://www.nlm.nih.gov/medlineplus/ency/article/000816.htm)
• Encyclopedia: Graves' disease (http://www.nlm.nih.gov/medlineplus/ency/article/000358.htm)
• Encyclopedia: Hashimoto's disease (http://www.nlm.nih.gov/medlineplus/ency/article/000371.htm)

• Educational resources - Information pages

• American Association of Clinical Endocrinologists (http://www.aace.com/pub/thyroidbrochures/)
• The National Women's Health Information Center: Graves' disease (http://www.4woman.gov/faq/graves.htm)
• The National Women's Health Information Center: Hashimoto's thyroiditis (http://www.4woman.gov/faq/hashimoto.htm)

You may also be interested in these resources, which are designed for genetics professionals and researchers.

• PubMed - Recent literature (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=PubMed&term=((TPO[TIAB])+OR+(thyroid+peroxidase[TIAB]))+AND+(iodide+peroxidase[MAJR])+AND+((Genes[MH])+OR+(Genetic+Phenomena[MH]))+AND+english[la]+AND+human[mh]&orig_db=PubMed&filters=ON&pmfilter_EDatLimit=1800+Days)
• OMIM - Genetic disorder catalog (http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=606765)
• Research Resources - Tools for researchers

• Atlas of Genetics and Cytogenetics in Oncology and Haematology (http://atlasgeneticsoncology.org/Genes/GC_TPO.html)
• Entrez Gene (http://view.ncbi.nlm.nih.gov/gene/7173)
• GeneCards (http://www.genecards.org/cgi-bin/carddisp.pl?gene=TPO)
• HUGO Gene Nomenclature Committee (http://www.genenames.org/data/hgnc_data.php?hgnc_id=12015)

References

• Abramowicz MJ, Targovnik HM, Varela V, Cochaux P, Krawiec L, Pisarev MA, Propato FV, Juvenal G, Chester HA, Vassart G. Identification of a mutation in the coding sequence of the human thyroid peroxidase gene causing congenital goiter. J Clin Invest. 1992 Oct;90(4):1200-4. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=1401057)
• Bakker B, Bikker H, Vulsma T, de Randamie JS, Wiedijk BM, De Vijlder JJ. Two decades of screening for congenital hypothyroidism in The Netherlands: TPO gene mutations in total iodide organification defects (an update). J Clin Endocrinol Metab. 2000 Oct;85(10):3708-12. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=11061528)
• Chardes T, Chapal N, Bresson D, Bes C, Giudicelli V, Lefranc MP, Peraldi-Roux S. The human anti-thyroid peroxidase autoantibody repertoire in Graves' and Hashimoto's autoimmune thyroid diseases. Immunogenetics. 2002 Jun;54(3):141-57. Epub 2002 May 03. Review. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=12073143)
• Kotani T, Umeki K, Kawano J, Suganuma T, Hishinuma A, Ieiri T, Harada S. Partial iodide organification defect caused by a novel mutation of the thyroid peroxidase gene in three siblings. Clin Endocrinol (Oxf). 2003 Aug;59(2):198-206. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=12864797)
• Nascimento AC, Guedes DR, Santos CS, Knobel M, Rubio IG, Medeiros-Neto G. Thyroperoxidase gene mutations in congenital goitrous hypothyroidism with total and partial iodide organification defect. Thyroid. 2003 Dec;13(12):1145-51. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=14751036)
• OMIM: thyroid peroxidase (http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=606765)
• Pannain S, Weiss RE, Jackson CE, Dian D, Beck JC, Sheffield VC, Cox N, Refetoff S. Two different mutations in the thyroid peroxidase gene of a large inbred Amish kindred: power and limits of homozygosity mapping. J Clin Endocrinol Metab. 1999 Mar;84(3):1061-71. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=10084596)
• Rivolta CM, Esperante SA, Gruneiro-Papendieck L, Chiesa A, Moya CM, Domene S, Varela V, Targovnik HM. Five novel inactivating mutations in the thyroid peroxidase gene responsible for congenital goiter and iodide organification defect. Hum Mutat. 2003 Sep;22(3):259. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&dopt=Abstract&list_uids=12938097)