What is ALT and AST?
ALT and AST are enzymes that are normally predominantly contained within liver cells. If the liver is injured or damaged, the liver cells spill these enzymes into the blood, raising the AST and ALT enzyme levels in the blood, and we can use it as a measurement of liver injury.
What are the differences between ALT and AST?
AST is normally found in a variety of tissues including liver, heart, muscle, kidney, and the brain. It is released into the serum when any one of these tissues is damaged. Therefore, it is not a highly specific indicator of liver injury as its elevation can occur as a result of other injured tissues.
On the other hand, ALT are largely found only in the liver cells. This is not to say that it is exclusively located in the liver, but that is where it is most concentrated. It is released into the bloodstream as the result of liver injury. Thus, it is thought to be a specific indicator to liver injury.
What does elevated ALT and AST levels mean?
Because 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 (but often does) indicate that there is a liver problem. For example, even vigorous exercise may elevate AST levels in the body. On the other hand, ALT are largely found only in the liver, ALT is a more accurate indication of liver injury.
A high ALT level can simply mean liver cells are being damaged, if high ALT level only happen over a short period of time it might not be a big problem as there are many different reasons that could cause injury to liver cells and as long as it is not a long term or chronic problem the liver can heal itself.
But if ALT level is elevated over a long period (more than 3 months) of time at a high level, then it is likely that there is a condition of liver problem causing long term liver injury/ inflammation and treatment is most likely needed.
Different ALT/ AST ration indicate different liver problem.
The ratio of the ALT and AST may also provide useful information regarding the extent and cause of liver disease. Most liver diseases are characterized by greater ALT elevations than AST elevations. Two exceptions to this rule exist. Both cirrhosis and/or alcohol abuse are associated with higher AST levels than ALT levels, often in a ratio of approximately 2:1.
What can causes high ALT and AST levels?
Elevations of ALT and AST could be due to a number of different reasons, additional testing is usually required to determine the exact problem. Some usual reasons of high ALT and AST level include:
- Viral hepatitis
- Fatty liver / NASH
- Alcoholic liver disease
- Medication induced liver disease
- Autoimmune hepatitis
- Liver tumors
- * All research and clinical data should be used as reference purposes only, results may vary.