Your liver performs hundreds of metabolic tasks. Numerous specialized proteins called enzymes propel these biochemical processes. Although the liver contains many different enzymes, high liver enzyme levels typically refers to a group of 2 to 5 enzymes present in particularly high concentrations. Elevated liver enzymes often indicate liver cell damage, which can occur with a wide array of conditions of varying severity. Transient, mild increases are relatively common and rarely cause lasting health effects. Persistent or marked increases in liver enzyme levels, however, may indicate a potentially serious medical disorder.
Liver Enzymes and Evaluation
Elevated liver enzymes generally refers to increased levels of one or more of the following enzymes:
- Alanine transaminase (ALT)
- Aspartate transaminase (AST)
- Alkaline phosphatase (ALP)
- Gamma-glutamyl transferase (GGT)
- Lactate dehydrogenase (LDH)
When liver cell injury occurs, these enzymes leak from the damaged cells causing elevated blood levels. Healthcare providers evaluate the levels of these enzymes relative to one another, blood levels other substances related to liver health, as well as a physical examination and possibly additional diagnostic tests to determine the cause of elevated liver enzymes.
Hepatitis -- inflammation of the liver -- is the leading cause of elevated liver enzymes. Many disorders and conditions cause of hepatitis, including:
- Excess alcohol use
- Hepatitis virus infection (A, B, C, D and E)
- Other viral infections, such as infectious mononucleosis
- Fatty liver disease
- Autoimmune hepatitis
- Medications, toxins and poisons
Hepatitis can be acute (occurs suddenly and lasts less than 6 months) or chronic (persists for longer than 6 months). Acute hepatitis sometimes leads to severe liver injury and failure, a condition called fulminant hepatitis. Chronic hepatitis can scar the liver over time, which may eventually result in cirrhosis.
Other Liver, Digestive and Systemic Disorders
Conditions that block bile flow from the liver to the gallbladder or intestine -- collectively known as bililary disorders -- often cause elevated liver enzymes. Examples of these disorders include:
- Chronic pancreatitis (inflammation of the pancreas)
- Tumor or cyst of the gallbladder or bile ducts
- Sclerosing cholangitis (inflammatory scarring of the bile ducts)
Whereas hepatitis refers to generalized liver inflammation, liver granulomas are localized areas of inflammation, which may cause elevated liver enzymes. These can occur for a variety of reasons including: certain infections (tuberculosis, syphilis, cat-scratch fever, etc.), medications (allopurinol, quinidine, etc.) and connective tissue disorders (sarcoidosis, etc.)
Other liver, digestive and systemic disorders that might cause elevated liver enzymes include:
- Hemochromatosis: iron overload, usually an inherited disorder
- Wilson disease: inherited condition that leads to copper overload
- Inflammatory bowel disease: ulcerative colitis and Crohn disease
- Thyroid disease: hypothyroidism and hyperthyroidism
- Cancer that arises or spreads to the liver
- Hodgkin lymphoma
- Systemic lupus erythematosus
- Anorexia nervosa
- Alpha-1-antitrypsin deficiency
While so-called liver enzymes are present in high concentrations in the liver, large amounts also exist in other body tissues. Therefore, elevations of certain liver enzymes might be due to non-liver-related causes. For example, strenuous physical exercise can cause a temporary increase in ALT, AST and LDH levels. Bone, small bowel and kidney diseases often cause elevated ALP levels.
Many commonly used over-the-counter and prescription medications can potentially cause elevated liver enzyme levels, including:
- Acetaminophen (Tylenol)
- Nonsteroidal anti-inflammatory drugs, such as diclofenac (Voltaren)
- Cholesterol-lowering statin drugs, such as atorvastatin (Lipitor), rosuvastatin (Crestor) and simvastatin (Zocor)
- Estrogens and oral contraceptives
- Antibiotics, such amoxicillin-clavulanate (Augmentin) and tetracycline
- Antiepileptics, such as phenytoin (Dilantin), carbamazepine (Tegretol) and valproic acid (Depakote)
Some herbs can also cause liver enzyme elevations and potentially serious liver injury, including germander, chaparral, valerian, skullcap, amanita, pennyroyal, greater celandine, kava, black cohosh, ma huang and jin bu huan.
The best course of action with a finding of elevated liver enzymes differs based in individual circumstances. Talk with your doctor if you have any questions or concerns.
Reviewed and revised by: Tina M. St. John, M.D.
- Merck Manual Professional Version: Causes of Hepatitis
- Merck Manual Professional Version: Overview of Iron Overload
- Merck Manual Professional Version: Hepatic Granulomas
- Canadian Medical Association Journal: Liver enzyme alteration: A Guide for Clinicians
- Ferri's Differential Diagnosis: A Practical Guide to the Differential Diagnosis of Symptoms, Signs, and Clinical Disorders; Fred F. Ferri
- Cleveland Clinic Journal of Medicine: When and How to Evaluate Mildly Elevated Liver Enzymes in Apparently Healthy Patients
- LiverTox: Herbal and Dietary Supplements