Liver enzymes are proteins inside your liver cells. The enzymes help your liver perform its functions, which include getting rid of toxins, processing medicines, storing and releasing sugars, and storing vitamins and minerals. Liver enzymes can be measured to assess the health of the liver and to follow the progression and improvement of liver diseases.
Types
There are several liver enzymes that can be measured in the blood. In general, these enzymes leak from the liver cells into the blood when the cells are damaged by infection, inflammation, or trauma. The most commonly measured liver enzymes are AST, or aspartate aminotransferase; ALT, or alanine aminotransferase; and ALP, or alkaline phosphatase
Function
The levels of these enzymes in the blood, as determined by testing, help your physician estimate the amount of liver damage caused by infection or inflammation. Several blood tests, like the hepatic or liver panel, measure the levels of these enzymes. ALT is mostly found in the liver and is the most useful test to detect and follow liver damage. The level of ALT will go up even before there are any physical signs of liver damage. AST is also mostly found in the liver, but it is also present in muscle and kidney cells. This means that an elevation of AST levels is not specific to liver damage, but can also occur in cases of muscle injury or kidney disease.
Causes
The causes of elevated liver enzymes are numerous. They include infection with viruses such as the hepatitis viruses, including hepatitis A, B and C; the Epstein-Barr virus, which causes infectious mononucleosis; and the herpes viruses. Other causes of elevated liver enzymes include alcoholic liver disease, cirrhosis, or scarring, of the liver with chronic inflammation, liver cancer, and autoimmune hepatitis, in which the body mistakenly attacks the liver as foreign tissue.
Symptoms
The symptoms of liver damage and elevated liver enzymes include abdominal pain, especially in the right upper segment of the abdomen where the liver is located; nausea and vomiting; and jaundice, a yellowish tinge of the skin and the whites of the eyes that results from the accumulation of bilirubin, a breakdown product that the healthy liver usually eliminates but that the damaged liver is unable to clear.
Considerations
In cases of acute hepatitis, the ALT level can stay elevated for one to two months and then return to normal over a few more months. According to Lab Tests Online, in most instances of liver damage, the ALT is higher than the AST, but the AST can be higher in cases of alcoholic liver disease and liver cirrhosis.
