Liver cells contain high concentrations of certain enzymes, or proteins, that facilitate chemical reactions. Liver cell injury causes leakage of these enzymes into the bloodstream, leading to abnormal elevations in the levels of these proteins. Doctors frequently order blood tests to measure liver enzyme levels as a method of screening for liver disease or monitoring known liver disease activity.
Alcoholic Liver Disease
Chronic excessive alcohol intake inflames and damages liver cells, causing an elevation in the liver enzyme levels. Alcohol and its breakdown products alter the metabolism within liver cells, triggering a cascade of chemical reactions that result in significant damage or death of the liver cells. Alcohol abuse causes a spectrum of liver disease, beginning with alcoholic fatty liver, progressing to alcoholic hepatitis and culminating in alcoholic cirrhosis, explains the Cleveland Clinic.
At each stage of alcoholic liver disease, elevations of the liver enzymes typically occur. With advanced liver cirrhosis, the liver enzymes may decrease as the functional liver tissue progressively shrinks and is replaced by scar tissue.
Viral Hepatitis
Viral hepatitis is an inflammation of the liver caused by infection with one or more viruses. Viral infection of the liver provokes direct and immune system-mediated damage to the liver cells, leading to elevated liver enzyme levels. Common liver-specific, or hepatotropic, viruses in the United States include hepatitis A, hepatitis B and hepatitis C, reports the Centers for Disease Control and Prevention. Hepatitis A causes a limited, acute hepatitis. Hepatitis B can cause acute or chronic hepatitis. Hepatitis C typically provokes chronic hepatitis.
Systemic virus can also infect the liver, causing varying degrees of liver inflammation, damage and liver enzyme elevations. The National Institute of Diabetes and Digestive and Kidney Diseases notes that non-hepatotropic viruses that may cause transient hepatitis include Epstein-Barr virus, which causes infectious mononucleosis, herpesvirus, cytomegalovirus, adenovirus and parvovirus.
Hemochromatosis
Hemochromatosis is a condition caused by iron overload, leading to destructive accumulation of iron in the body tissues, explains the National Heart, Lung and Blood Institute. The liver is a primary site of iron storage and bears much of the damage associated with hemochromatosis. As iron accumulates in the liver cells, metabolism is adversely affected, causing damage and eventual destruction of the cells with an accompanying increase in liver enzyme levels.
Early in the course of hemochromatosis, elevated liver enzyme levels may be the first sign of disease. The National Heart, Lung and Blood Institute reports that approximately 1 million people in the United States have hereditary hemochromatosis, making this condition one of the most prevalent genetic diseases among Americans.
References
- Cleveland Clinic: Alcoholic Liver Disease
- Centers for Disease Control and Prevention: Viral Hepatitis
- National Institute of Diabetes and Digestive and Kidney Diseases: Viral Hepatitis: A Through E and Beyond
- National Heart, Lung and Blood Institute: Hemochromatosis
- "Harrison's Principles of Internal Medicine, 16th Edition"; Dennis L. Kasper, M.D., et al., Editors; 2004
