Aminotransferases are enzymes (proteins that help speed up chemical reactions in the body) that are found mainly in the liver, but also in other tissues, such as muscles. They are a part of the normal metabolic processes in the liver and are responsible for transferring amino acids (components that build proteins) from one molecule to another. ALT was formerly known as serum glutamic-pyruvic transaminase (SGPT) and AST as serum glutamic-oxaloacetic transaminase (SGPT).
The ALT and AST levels are obtained directly from a blood sample that is sent to the laboratory for measurement. The results are usually available within hours to days and are reported to the ordering doctor for review.
Normal Levels of AST and ALT. Normal levels of AST and ALT may slightly vary depending on the individual laboratory’s reference values. Typically the range for normal AST is reported between 10 to 40 units per liter and ALT between 7 to 56 units per liter. Mild elevations are generally considered to be 2-3 times higher than the normal range. In some conditions, these enzymes can be severely elevated, in the 1000s range.
Diseases That Cause Abnormal Aminotransferase Levels. The most common diseases causing abnormally elevated ALT and AST are:
Acute viral hepatitis, such as hepatitis A or B
Chronic viral hepatitis, such hepatitis B or C
Cirrhosis of the liver (scarring of the liver due to long standing inflammation of the liver)
Liver damage from alcohol abuse or alcoholic fatty liver
Hemochromatosis (a genetic condition causing long standing liver damage due to iron build up in the liver)
Less Common Causes of Abnormal Aminotransferase Levels. There are many other causes of the abnormally elevated blood liver enzyme levels in addition to those mentioned above. Some of these conditions include the following:
Wild mushroom poisoning
Wilson’s disease, due to excess buildup of copper in the liver
Metastatic cancer to the liver (cancer spread from another organ to the liver)
Cancer of the liver (hepatocellular carcinoma)
Auto-attack immune hepatitis (the body’s own immune system attack the liver cells)
Monitoring ALS and ALT Levels. Monitoring of the liver tests depends on the degree, the duration, and the cause of the abnormality. For example, in a person who has chronic (long standing) hepatitis B or C infection, the liver specialist (hepatologist) may opt for surveillance of these levels every 3 to 6 months to ensure that they are not rising.