TH gene

The TH gene provides instructions for producing the enzyme tyrosine hydroxylase, which is essential for the synthesis of chemical messengers in the nervous system.

Normal Function

The TH gene provides instructions for making the enzyme tyrosine hydroxylase. This enzyme facilitates the first step in the pathway that produces catecholamines, a group of chemical messengers including dopamine, norepinephrine, and epinephrine.

Catecholamines are vital for the autonomic nervous system, which regulates involuntary processes such as blood pressure and body temperature. They are released in response to stress and transmit signals between brain cells and other cells in the body. Tyrosine hydroxylase specifically helps convert the amino acid tyrosine to L-DOPA, which is then converted into dopamine.

Health Conditions Related to Genetic Changes

Dopa-responsive dystonia

Variants in the TH gene can cause TH-deficient dopa-responsive dystonia. This condition involves involuntary muscle contractions (dystonia), tremors, and other uncontrolled movements. These symptoms typically respond to treatment with L-Dopa. Most variants associated with this condition reduce the activity of the tyrosine hydroxylase enzyme, leading to decreased dopamine production.

Tyrosine hydroxylase deficiency

Many variants in the TH gene are associated with tyrosine hydroxylase deficiency, a condition that primarily affects movement and varies in severity. These variants reduce the activity of the tyrosine hydroxylase enzyme, resulting in lower levels of dopamine, norepinephrine, and epinephrine. The resulting imbalance of these catecholamines contributes to nervous system dysfunction and abnormal movements.