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TH gene

tyrosine hydroxylase

Normal Function

The TH gene provides instructions for making the enzyme tyrosine hydroxylase, which is important for the normal functioning of the nervous system. Tyrosine hydroxylase takes part in the first step of the pathway that produces a group of chemical messengers called catecholamines.

Catecholamines are involved in the autonomic nervous system, which controls involuntary processes such as the regulation of blood pressure and body temperature. Catecholamines are released into the body in response to physical or emotional stress. Catecholamines also transmit signals from brain cells to other cells in the body.

Tyrosine hydroxylase helps convert the protein building block (amino acid) tyrosine to L-DOPA, which can then be converted to dopamine. Other catecholamines called norepinephrine and epinephrine are produced from dopamine.

Health Conditions Related to Genetic Changes

Dopa-responsive dystonia

Several variants (also called mutations) in the TH gene have been found to cause a form of dopa-responsive dystonia called TH-deficient dopa-responsive dystonia. This condition is characterized by a pattern of involuntary muscle contractions (dystonia), tremors, and other uncontrolled movements. These symptoms usually respond to treatment with a medication called L-Dopa.

Most TH gene variants that cause this condition change single amino acids in the tyrosine hydroxylase enzyme. These changes reduce the activity of tyrosine hydroxylase, which leads to a decrease in the production of dopamine and causes the movement problems seen in people with TH-deficient dopa-responsive dystonia.

Dopa-responsive dystonia caused by variants in the TH gene is often considered a mild form of tyrosine hydroxylase deficiency.

More About This Health Condition

Tyrosine hydroxylase deficiency

Many variants in the TH gene have been identified in people with tyrosine hydroxylase deficiency.  This is a condition that primarily affects movement and can vary in severity. The TH gene variants that cause tyrosine hydroxylase deficiency reduce the 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. Changes in their levels contribute to the abnormal movements and nervous system dysfunction seen in people with tyrosine hydroxylase deficiency.

In general, the severity of tyrosine hydroxylase deficiency cannot be predicted based on the specific variant. However, individuals who have two variants in the region of DNA that controls the activity of the TH gene (promoter region) do not typically develop the most severe form of tyrosine hydroxylase deficiency.

More About This Health Condition

Other Names for This Gene

  • DYT5b
  • 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

Gene and Variant Databases


  • Furukawa Y, Kish S. Tyrosine Hydroxylase Deficiency. 2008 Feb 8 [updated 2017 May 11]. In: Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Bean LJH, Gripp KW, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Available from 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. doi: 10.1002/ana.10820. No abstract available. Citation on PubMed
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  • 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. doi: 10.1212/01.wnl.0000142083.47927.0a. 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. doi: 10.1002/ana.21199. 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

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.