Skip Navigation
Genetics Home Reference: your guide to understanding genetic conditions About   Site Map   Contact Us
 
Home A service of the U.S. National Library of Medicine®
 
 
Printer-friendly version
TH

TH

Reviewed May 2012

What is the official name of the TH gene?

The official name of this gene is “tyrosine hydroxylase.”

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

Read more about gene names and symbols on the About page.

What is the normal function of the TH gene?

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.

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

dopa-responsive dystonia - caused by mutations in the TH gene

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.

tyrosine hydroxylase deficiency - caused by mutations in the TH gene

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.

other disorders - associated with the TH gene

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.

Where is the TH gene located?

Cytogenetic Location: 11p15.5

Molecular Location on chromosome 11: base pairs 2,163,928 to 2,171,804

The TH gene is located on the short (p) arm of chromosome 11 at position 15.5.

The TH gene is located on the short (p) arm of chromosome 11 at position 15.5.

More precisely, the TH gene is located from base pair 2,163,928 to base pair 2,171,804 on chromosome 11.

See How do geneticists indicate the location of a gene? in the Handbook.

Where can I find additional information about TH?

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

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

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

  • DYT5b
  • TY3H_HUMAN
  • TYH
  • tyrosine 3-monooxygenase

Where can I find general information about genes?

The Handbook provides basic information about genetics in clear language.

These links provide additional genetics resources that may be useful.

What glossary definitions help with understanding TH?

acids ; allele ; amino acid ; autonomic nervous system ; deficiency ; dopamine ; dystonia ; enzyme ; gene ; hypertension ; involuntary ; nervous system ; neurological ; polymorphism ; protein ; spectrum ; stress ; syndrome ; tyrosine

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

See also Understanding Medical Terminology.

References (15 links)

 

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.

 
Reviewed: May 2012
Published: December 16, 2014