Medical professionals order liver function tests to evaluate overall liver health. With liver function tests, the laboratory measures the levels of certain proteins and chemicals in the blood. Abnormally high liver function test results may indicate an underlying liver problem. Many conditions can cause elevated liver function tests, including inflammation, infections and reactions to toxins and medications. Additional blood tests and diagnostic procedures help doctors determine the underlying cause of abnormally high liver function tests.
Viral Hepatitis
Several species of viruses preferentially infect the liver, causing inflammation and liver cell damage. The most common hepatitis viruses in the United States are hepatitis A, B and C, according to the Centers for Disease Control and Prevention. Hepatitis A is primarily a food-borne infection. Hepatitis B and C are blood-borne viruses. Sexual and mother-to-child transmission predominate for hepatitis B. Sharing injection drug equipment remains the leading cause of hepatitis C infections.
All forms of viral hepatitis can cause acute hepatitis with elevated liver function tests. Hepatitis B and C can persist in the liver, causing chronic hepatitis with progressive liver scarring. Liver function tests among people with chronic viral hepatitis often remain persistently elevated, although the degree of elevation does not necessarily reflect the severity of the underlying liver disease, notes the American Gastroenterological Association.
Noninfectious Hepatitis
Many noninfectious illnesses and conditions can cause liver inflammation, or hepatitis. Alcoholic liver disease is a leading cause of hepatitis and cirrhosis in the United States. In a January 2010 article published in the "American Journal of Gastroenterology," Dr. Robert O'Shea and colleagues note that in 2003, approximately 44 percent of all liver disease-related deaths in the United States were attributable to excessive alcohol consumption. People with alcoholic liver disease typically have elevated liver function tests, which may be the first sign of alcohol-induced liver damage.
Nonalcoholic fatty liver disease is an increasingly common cause of noninfectious hepatitis among Americans. An abnormal accumulation of fat in the liver cells can provoke an inflammatory reaction, leading to liver cell damage. This condition, known as nonalcoholic steatohepatitis or NASH, may cause progressive liver scarring and cirrhosis. NASH most commonly occurs in people who are overweight or obese and have prediabetes or diabetes, reports the American College of Gastroenterology. People with nonalcoholic fatty liver disease are typically asymptomatic early in the course of the illness. Doctors frequently diagnose the condition because of abnormally elevated liver function tests detected during routine health screening.
Biliary Disease
Liver cells produce bile, which flows through a system of ducts to the gallbladder. The gallbladder stores the bile until its release through the common bile duct into the small intestine. Abnormalities in bile production or transport can lead to liver disease and elevated liver function tests. "Harrison's Principles of Internal Medicine" notes that biliary diseases frequently associated with abnormal liver function tests include gallstone obstruction of the common bile duct, primary biliary cirrhosis and cholangitis, an inflammation of the bile duct system. Medications can also adversely affect the biliary system, including captopril, allopurinol, tolbutamide, nevirapine, indinivir, erythromycin and estrogens.
References
- Centers for Disease Control and Prevention: Viral Hepatitis
- Centers for Disease Control and Prevention: The ABCs of Hepatitis
- Gastroenterology: American Gastroenterological Association Medical Position Statement--Evaluation of Liver Chemistry Tests
- "American Journal of Gastroenterology"; Alcoholic Liver Disease; Robert S. O' Shea, M.D., et al.; January 2010
- The American College of Gastroenterology: Fatty Liver Disease
