High levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the blood often signal an underlying health issue. These enzymes, normally found inside cells, indicate cell damage or injury when present in the bloodstream above typical levels. Doctors frequently order ALT and AST tests during routine check-ups or when symptoms suggest a problem.
The Role of ALT and AST
ALT and AST are enzymes involved in amino acid metabolism. ALT is predominantly found in the liver, making it a more specific indicator of liver cell damage. AST is present in a wider range of tissues, including the liver, heart, skeletal muscles, kidneys, brain, and red blood cells.
When cells are damaged, their membranes can become compromised, leading to ALT and AST leakage into the bloodstream. Detecting elevated levels suggests cellular integrity has been disrupted in one or more organs. The location and specific function of each enzyme provide initial clues about the potential source of the damage.
What Elevated Levels Suggest
Elevated ALT and AST levels primarily suggest cell damage or injury, with the liver often being the primary concern. Compromised liver cells release these enzymes into the blood, indicating inflammation, stress, or direct injury.
While ALT is specific to the liver, elevated AST levels, due to its broader distribution, can also point to damage in other tissues. If both ALT and AST are elevated, it strongly suggests a liver problem.
Common Causes of Elevation
Many conditions can lead to elevated ALT and AST levels, with liver-related issues being the most frequent. Non-alcoholic fatty liver disease (NAFLD), where fat accumulation in the liver can lead to inflammation and cell damage, is a common cause. Alcoholic liver disease also frequently results in elevated enzymes, as excessive alcohol consumption directly harms liver cells.
Viral hepatitis, caused by viruses like hepatitis A, B, or C, leads to liver inflammation and can cause significant increases in both ALT and AST. Certain medications, supplements, and even over-the-counter pain relievers can induce drug-induced liver injury, causing enzyme levels to rise. Cirrhosis, which is advanced scarring of the liver, can also present with elevated transaminases, although in late stages, levels might normalize despite severe damage.
Other conditions like hemochromatosis (excessive iron accumulation) and autoimmune hepatitis (immune system attacking liver cells) also typically present with highly elevated ALT and AST. Beyond the liver, strenuous exercise, muscle injury or diseases, and hypothyroidism can similarly cause increases in these enzyme levels.
Interpreting Your Results and Next Steps
Interpreting elevated ALT and AST results involves considering several factors beyond just the numerical values. The degree of elevation, whether mild, moderate, or severe, provides important clues about the underlying cause. A very high elevation, for instance, might suggest acute viral hepatitis or severe drug-induced injury.
The ratio of AST to ALT can also offer insights. An AST:ALT ratio of 2:1 or greater often suggests alcoholic liver disease, particularly if gamma-glutamyl transferase (GGT) is also elevated. Conversely, in many other forms of liver injury, such as non-alcoholic fatty liver disease or chronic viral hepatitis, ALT levels are typically higher than AST, resulting in a ratio less than 1. It is also important to note that a high AST with normal ALT could indicate a problem outside the liver, such as muscle or heart conditions.
Temporary factors like recent intense exercise, certain medications, or alcohol intake can influence enzyme levels, meaning a single high reading does not always indicate severe disease. Therefore, a healthcare professional is crucial for accurately interpreting results within the context of a person’s overall health, symptoms, and medical history. Follow-up actions may include repeat testing, additional blood tests to assess other liver functions, imaging studies like an ultrasound, or referrals to specialists for further evaluation. These steps help to pinpoint the cause and guide appropriate management.