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TH gene

tyrosine hydroxylase
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Normal Function

The TH gene provides instructions for making the enzyme tyrosine hydroxylase, which is important for normal functioning of the nervous system. Tyrosine hydroxylase takes part in the first step of the pathway that produces a group of hormones called catecholamines. This enzyme helps convert the protein building block (amino acid) tyrosine to a catecholamine called dopamine. Dopamine is also known as a neurotransmitter because it transmits signals between nerve cells in the brain to help control physical movement and emotional behavior. Other catecholamines called norepinephrine and epinephrine are produced from dopamine. Norepinephrine and epinephrine are involved in the autonomic nervous system, which controls involuntary body processes such as the regulation of blood pressure and body temperature.

Health Conditions Related to Genetic Changes

Dopa-responsive dystonia

More than two dozen mutations in the TH gene have been found to cause dopa-responsive dystonia. This condition is characterized by a pattern of involuntary muscle contractions (dystonia), tremors, and other uncontrolled movements and usually responds to treatment with a medication called L-Dopa. Most TH gene mutations that cause this condition change single protein building blocks (amino acids) in the tyrosine hydroxylase enzyme, resulting in a decrease in functional enzyme. A reduction in normal tyrosine hydroxylase enzyme leads to a decrease in the production of dopamine, which causes the movement problems characteristic of dopa-responsive dystonia. The amount of functional enzyme that is produced is associated with the severity of the signs and symptoms. Less functional enzyme leads to more severe symptoms.

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Tyrosine hydroxylase deficiency

More than 20 mutations in the TH gene have been identified in people with tyrosine hydroxylase (TH) deficiency. These mutations result in reduced activity of the tyrosine hydroxylase enzyme. As a result, the body produces less dopamine, norepinephrine, and epinephrine. These catecholamines are necessary for normal nervous system function, and changes in their levels contribute to the abnormal movements, nervous system dysfunction, and other neurological problems seen in people with TH deficiency.

Dopa-responsive dystonia is sometimes considered a mild form of tyrosine hydroxylase deficiency. It is uncertain whether they are two separate disorders or part of the same disease spectrum.

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Other disorders

Certain common TH variations (polymorphisms) modify catecholamine production, which affects the risk of developing conditions associated with regulation of the autonomic nervous system. These TH gene polymorphisms affect the extent to which blood pressure increases with stress and may increase the risk of high blood pressure (hypertension).

One TH gene polymorphism has been associated with sudden infant death syndrome (SIDS). SIDS is a major cause of death in babies younger than 1 year. It is characterized by sudden and unexplained death, usually during sleep. The polymorphism, called allele *9.3, is the most common TH gene polymorphism among people of European descent and has been identified in a larger percentage of babies who die from SIDS than in other babies. This version of the gene may affect the regulation of breathing or awakening in infants.

Other Names for This Gene

  • DYT5b
  • TY3H_HUMAN
  • TYH
  • tyrosine 3-monooxygenase

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Research Resources

References

  • Furukawa Y, Kish S. Tyrosine Hydroxylase Deficiency. 2008 Feb 8 [updated 2017 May 11]. In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2020. Available from http://www.ncbi.nlm.nih.gov/books/NBK1437/ Citation on PubMed
  • Furukawa Y, Kish SJ, Fahn S. Dopa-responsive dystonia due to mild tyrosine hydroxylase deficiency. Ann Neurol. 2004 Jan;55(1):147-8. Citation on PubMed
  • Hoffmann GF, Assmann B, Bräutigam C, Dionisi-Vici C, Häussler M, de Klerk JB, Naumann M, Steenbergen-Spanjers GC, Strassburg HM, Wevers RA. Tyrosine hydroxylase deficiency causes progressive encephalopathy and dopa-nonresponsive dystonia. Ann Neurol. 2003;54 Suppl 6:S56-65. Citation on PubMed
  • Hunt SC. Tyrosine hydroxylase: another piece of the genetics of hypertension puzzle. Circulation. 2007 Aug 28;116(9):970-2. Citation on PubMed
  • Klintschar M, Reichenpfader B, Saternus KS. A functional polymorphism in the tyrosine hydroxylase gene indicates a role of noradrenalinergic signaling in sudden infant death syndrome. J Pediatr. 2008 Aug;153(2):190-3. doi: 10.1016/j.jpeds.2008.02.032. Epub 2008 Apr 3. Citation on PubMed
  • Pearl PL, Capp PK, Novotny EJ, Gibson KM. Inherited disorders of neurotransmitters in children and adults. Clin Biochem. 2005 Dec;38(12):1051-8. Epub 2005 Nov 18. Review. Citation on PubMed
  • Pearl PL, Taylor JL, Trzcinski S, Sokohl A. The pediatric neurotransmitter disorders. J Child Neurol. 2007 May;22(5):606-16. Review. Citation on PubMed
  • Rao F, Zhang L, Wessel J, Zhang K, Wen G, Kennedy BP, Rana BK, Das M, Rodriguez-Flores JL, Smith DW, Cadman PE, Salem RM, Mahata SK, Schork NJ, Taupenot L, Ziegler MG, O'Connor DT. Adrenergic polymorphism and the human stress response. Ann N Y Acad Sci. 2008 Dec;1148:282-96. doi: 10.1196/annals.1410.085. Citation on PubMed or Free article on PubMed Central
  • Rao F, Zhang L, Wessel J, Zhang K, Wen G, Kennedy BP, Rana BK, Das M, Rodriguez-Flores JL, Smith DW, Cadman PE, Salem RM, Mahata SK, Schork NJ, Taupenot L, Ziegler MG, O'Connor DT. Tyrosine hydroxylase, the rate-limiting enzyme in catecholamine biosynthesis: discovery of common human genetic variants governing transcription, autonomic activity, and blood pressure in vivo. Circulation. 2007 Aug 28;116(9):993-1006. Epub 2007 Aug 13. Citation on PubMed
  • Schiller A, Wevers RA, Steenbergen GC, Blau N, Jung HH. Long-term course of L-dopa-responsive dystonia caused by tyrosine hydroxylase deficiency. Neurology. 2004 Oct 26;63(8):1524-6. Citation on PubMed
  • Verbeek MM, Steenbergen-Spanjers GC, Willemsen MA, Hol FA, Smeitink J, Seeger J, Grattan-Smith P, Ryan MM, Hoffmann GF, Donati MA, Blau N, Wevers RA. Mutations in the cyclic adenosine monophosphate response element of the tyrosine hydroxylase gene. Ann Neurol. 2007 Oct;62(4):422-6. Citation on PubMed
  • Yeung WL, Wong VC, Chan KY, Hui J, Fung CW, Yau E, Ko CH, Lam CW, Mak CM, Siu S, Low L. Expanding phenotype and clinical analysis of tyrosine hydroxylase deficiency. J Child Neurol. 2011 Feb;26(2):179-87. doi: 10.1177/0883073810377014. Epub 2010 Sep 7. Erratum in: J Child Neurol. 2012 Jun;27(6):829-31. Citation on PubMed
  • Zhang L, Rao F, Wessel J, Kennedy BP, Rana BK, Taupenot L, Lillie EO, Cockburn M, Schork NJ, Ziegler MG, O'Connor DT. Functional allelic heterogeneity and pleiotropy of a repeat polymorphism in tyrosine hydroxylase: prediction of catecholamines and response to stress in twins. Physiol Genomics. 2004 Nov 17;19(3):277-91. Epub 2004 Sep 14. Citation on PubMed
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