The liver, one of the largest organs in the body, is located in the upper right region of the abdomen, below the rib cage. The main function of the liver is to detoxify the blood, filtering drugs, medicines and other substances that could potentially be harmful. When the liver is damaged, its cells release enzymes into the bloodstream that can be measured in a blood test.
The Facts
The most commonly measured liver enzymes are alanine transaminase, or ALT, and aspartate transaminase, or AST. ALT is found mostly in the liver and, according to Lab Tests Online, is an indicator of liver inflammation or hepatitis. AST is present in the liver but also in other organs such as the heart. Another commonly measured liver enzyme is alkaline phosphatase of ALP, found mostly within the bile ducts, the tiny tubules that drain bile that's produced in the liver into the intestine.
Causes
According to MayoClinic.com, many diseases and conditions can cause liver damage and elevation of liver enzymes. The most common causes are infection with the hepatitis viruses; fatty liver disease, in which fat accumulates in the liver, because of chronic alcohol abuse or a high-cholesterol, high-fat diet, among other causes; obesity; and some over-the-counter medications, like acetaminophen.
Considerations
Liver enzymes levels are used to detect liver damage but also to screen for infections such as hepatitis; to monitor the progression of chronic diseases such as alcoholism, liver cancer, and gall bladder disease; to verify that a treatment for liver damage is working; and to measure the side effects of certain medications.
Symptoms
The symptoms of liver damage depend on the cause of the illness. In general, liver disease causes weakness, loss of appetite, nausea and vomiting and abdominal pain and swelling. Liver disease also causes jaundice, a yellowish tint of the skin and the whites of the eyes, which results from the accumulation of bilirubin. Bilirubin is a yellowish pigment, a by-product of the breakdown of red blood cells which accumulates when the liver loses its ability to process it.
Warning
In most cases of liver damage, ALT is more elevated than AST. This is not the case when the liver damage is caused by chronic alcoholism and liver cirrhosis, or scarring of the liver. In some cases, the liver enzymes may not reflect liver damage. ALT and AST levels can be normal in cases of cancer that has spread to the liver or in cases of gallbladder disease.
