Alanine Aminotransferase

Alanine aminotransferase (ALT) is an enzyme found in the kidneys, heart, and skeletal muscle tissue but primarily in liver tissue. It functions as a catalyst in the reaction needed for amino acid production. The test is used mainly in the diagnosis of liver disease and to monitor the effects of hepatotoxic drugs.
ALT is assessed along with asparate aminotransferase (AST) in monitoring liver damage. These two values normally exist in an approximately 1:1 ratio. The AST is greater than the ALT in alcohol-induced hepatitis, cirrhosis, and metastatic cancer of the liver. ALT is greater than AST in the case of viral or drug-induced hepatitis and hepatic obstruction due to causes other than malignancy.
The degree of increase in these enzyme levels provides information as to the possible source of the problem. A twofold increase is suggestive of an obstructive problem, often requiring surgical intervention. A 10-fold increase of ALT and AST indicates a probable medical problem such as hepatitis.