What Are the Causes of Having Elevated Liver Enzymes?
Mar 28, 2011 | By Jason Dority
Photo Credit Gary Gladstone/Creatas/Getty Images
Four primary liver enzymes can be elevated in the bloodstream, indicating possible damage to the liver. These include the transaminases AST and ALT, also known as aspartate aminotransferase and alanine aminotransferase, respectively and the cholestatic liver enzymes alkaline phosphatase and gamma-glutamyl transferase, or AP and GGT, respectively. The cause of elevated liver enzymes can be grouped into three categories -- cholestatic and hepatocellular liver injury and non-liver-damage related.
Bile Duct Injury
Injury or blockage of the bile ducts can impair the flow of bile -- a complex fluid that plays a role in fat digestion and waste removal -- through the ducts, a condition known as cholestasis. Collectively known as cholestatic liver injury or disease, this type of injury can elevate the liver enzymes GGT and AP. These enzymes leak out of the liver and into the bloodstream when bile flow is blocked and becomes backed up.
Many different conditions can injure the bile ducts leading to elevated liver enzymes. Inflammation of the liver due to fatty liver disease, or a build-up of fat in the liver, can damage the bile ducts as well as liver damage caused by primary biliary cirrhosis or primary sclerosing cholangitis. Cancer of the liver, gallstones and certain medications can also injury the bile ducts resulting in elevated liver enzymes.
Hepatocellular Liver Injury
Injury to the cells of the liver, known as hepatocellular liver injury, may cause elevated levels of the enzymes AST and ALT. This damage results in the leakage of AST and ALT into the bloodstream. Hepatocellular damage may be a result of many different conditions affecting the liver. Hepatitis or inflammation of the liver caused by a virus -- as in hepatitis C -- or drug or alcohol abuse can lead to the destruction of liver cells and elevated liver enzymes. Liver cell damage may also be caused by medications, liver tumors and genetic liver diseases such as hemochromatosis or Wilson's disease.
Non-liver Damage Elevations
The liver enzymes ALT and GGT are primarily found in the liver, but ALT and AP can also be found in high amounts in other organs. ALT is common in the kidneys, muscle and heart and AP can be found in the bones, intestines, kidneys and placenta. Therefore, elevated liver enzymes may not always indicated damage to the liver. Strenuous exercise or heart failure can temporarily elevate AST levels in the bloodstream. Other conditions that can raise liver enzyme levels that are not related to liver injury include celiac disease, hyperthyroidism and the muscle disease myopathy, according to an article in the March 2005 issue of "American Family Physician."