Alanine Aminotransferase (ALT) is an enzyme that is found predominantly in the liver; lesser quantities are found in the kidneys, heart, and skeletal muscle. Injury or disease affecting the liver parenchyma will cause a release of this hepatocellular enzyme into the bloodstream, thus elevating serum ALT levels.
Alanine Aminotransferase test is used to identify hepatocellular diseases of the liver. It is also an accurate monitor of improvement or worsening of these diseases. In jaundiced patients an abnormal alanine aminotransferase (ALT) will incriminate the liver rather than red blood cell (RBC) hemolysis as a source of the jaundice.
Most ALT elevations are caused by liver dysfunction. Therefore this enzyme is not only sensitive but also quite specific for hepatocellular disease. In hepatocellular disease other than viral hepatitis the ALT/AST (aspartate aminotransferase) ratio (DeRitis ratio) is less than 1. In viral hepatitis the ratio is greater than 1. This is helpful in the diagnosis of viral hepatitis.
Causes of False Alanine Aminotransferase Indications
Alanine Aminotransferase levels are sensitive to medications. The following is a list of medications that may increase Alanine Aminotransferase levels:
- Aminosalicylic Acid.
- Isoniazid (INH).
- Nalidixic acid.
- Oral Contraceptives.
High Alanine Aminotransferase Levels may occur if the patient is given an Intramuscular Injection prior to the test.
Normal Alanine Aminotransferase Levels
Alanine Aminotransferase levels are the highest among infants. Infant levels of ALT may normally reach as twice as ALT levels in adults. An elderly may also has a higher ALT level than an adult. As with several Liver enzymes, African Americans tend to normally have lower Alanine Aminotransferase levels than other races.
The normal Alanine Aminotransferase level range for both Adults and Children is between 4 to 36 international units/L at 37° C (98.6° F).
Causes of High Alanine Aminotransferase Levels
Injury or disease affecting the liver, heart, or skeletal muscles will cause a release of Alanine Aminotransferase into the bloodstream which mildly increase serum Alanine Aminotransferase levels. This mild increase in ALT levels can be an indication of :
- Myocardial infarction.
- Infectious mononucleosis.
Moderate increase in Alanine Aminotransferase levels can be caused by any of the following;
- Hepatic Tumor.
- Hepatotoxic Drugs.
- Obstructive Jaundice.
- Severe Burns.
- Trauma to Striated Muscl.
Significantly high Alanine Aminotransferase level can be an indication of Hepatitis, Hepatic necrosis, or Hepatic Ischemia.