AST and ALT (Transaminases)

These two enzymes, AST and ALT, are jointly known as transaminases. They are associated with inflammation or injury to liver cells. Damage to the liver typically results in a leak of AST and ALT into the bloodstream.
Since AST is found in many other organs besides the liver, including the kidneys, the muscles, and the heart, having a high level of AST does not always indicate that there is a liver problem.
However, high levels of transaminases in the blood don’t always reveal just how badly the liver is inflamed or damaged. The normal ranges for AST and ALT are around 0 to 40 IU/L and 0 to 45 IU/L respectively.
It is important to know that if the liver was damaged years before, by excessive alcohol use for example, the results of a blood test done today may be normal, but a damaged liver may still be present.
 
Males have higher transaminase levels than females. African-American men have higher AST levels compared with Caucasian men. Even the time of day that a blood sample is drawn may influence the level of transaminase elevation. People appear to have higher transaminase levels in the morning and afternoon than in the evening. Most liver diseases are characterized by greater ALT elevations than AST elevations. There are only two exceptions to this rule: both cirrhosis and alcohol abuse are associated with higher AST levels than ALT levels, often in a ratio of approximately 2:1.

Some possible causes of elevated transaminase levels include the following:

• Viral hepatitis
• A fatty liver
• Alcoholic liver disease
• Drug/medication-induced liver disease
• Autoimmune hepatitis
• Herbal toxicity
• Genetic liver diseases
• Liver tumors
• Heart failure
• Strenuous exercise