The liver is an important organ in the body, in charge of detoxifying the blood from medicines, chemicals and other substances, among other duties. Located in the right upper portion of the abdomen, right below the rib cage, it's one of the largest organs in the human body. When a person suffers from liver damage, enzymes inside the liver's cells leak out into the blood stream. This elevation of liver enzymes can then be measured and used to detect and monitor liver disease.
Types
There are two main liver enzymes: alanine transaminase, or ALT; and aspartate transaminase, or AST. According to Lab Tests Online, both enzymes are found in great quantities in the liver, although ALT is more prevalent. AST is also present in muscles and kidney tissue, making it a more specific test for the detection and monitoring of liver disease. Another liver enzyme, alkaline phosphatase, or ALP, helps in the detection of damage to the bile ducts, the tiny conduits within the liver used to transport bile to the gallbladder.
Causes
Many diseases and conditions can cause elevation of liver enzymes. According to MayoClinic.com, the most common causes are medications, both over-the-counter and prescription; viral hepatitis, or infection of the liver by various viruses; and nonalcoholic fatty liver disease, occurring in obese, overweight individuals. Other causes include autoimmune hepatitis, in which the body mistakes the liver for foreign tissue and attacks it, causing inflammation and loss of liver cells, alcoholism, pancreatitis and cancer.
Symptoms
Usually, people with elevated liver enzymes have symptoms that arouse a doctor's suspicion of the presence of liver disease. According to Lab Tests Online, these include weakness and fatigue, loss of appetite due to nausea and vomiting, abdominal pain and jaundice, a yellow tinge to the skin that indicates the liver is unable to process bilirubin. Other symptoms depend on the underlying conditions. For example, people with viral hepatitis may have fever, night sweat and chills; people with alcoholic liver disease may also suffer from easy bruising and prominent capillaries and other blood vessels.
Considerations
An ALT assay is a more sensitive test for detecting liver damage, although it can be elevated for other reasons. Likewise, AST is present in other body tissues, so an elevation of this enzyme does not necessarily point to liver disease. These tests are usually obtained as part of a panel of laboratory studies that can be correlated to detect the presence of liver damage.
Features
ALT is usually greatly increased in people with acute liver damage resulting from infections, drugs or toxins. People with chronic liver disease have a moderate elevation of this enzyme. AST is more elevated than ALT in people with alcoholic liver disease and cirrhosis, or scarring of the liver.
