Alanine Aminotransferase (ALT)

Alanine Aminotransferase (ALT) measurements are particularly useful in diagnosing and managing certain liver diseases, e.g., viral hepatitis and cirrhosis. ALT activity in tissue is generally much lower than aspartate aminotransferase (AST) activity and is found in the highest concentrations in the liver. Significant elevations of ALT occur only in diseases of the liver. ALT is often measured in conjunction with AST to determine whether the source of the AST is the liver or the heart. ALT usually is not elevated in cases of myocardial infarction, i.e., a normal ALT, in conjunction with an elevated AST, tends to suggest cardiac disease. However, slight ALT elevations may occur if an infarct destroys a large volume of the heart muscle.