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ALT is an enzyme found in the liver and other organs that is commonly monitored in blood tests to evaluate liver function. Elevated levels can indicate liver damage or disease, as well as other conditions. ALT participates in the glucose-alanine cycle, enabling efficient muscle contraction. Test results can be affected by various factors, including medications, exercise, and pregnancy.
Alanine aminotransferase (ALT) is an enzyme found primarily in the liver. It is also found in smaller quantities in other organs, such as the kidneys, heart, muscles and pancreas. Previously called serum glutamate pyruvic transaminase, ALT is now sometimes alternatively known as alanine transaminase. ALT is commonly monitored by doctors in blood test panels and is particularly useful in liver function tests.
The enzyme alanine aminotransferase participates in the alanine cycle in cells. As an enzyme, it is a protein produced by the body to speed up a chemical reaction. The specific function of ALT is to catalyze a reversible reaction that transfers an amino group from alanine to alpha-ketoglutarate, producing pyruvate and glutamate. ALT activity is highest in hepatocytes, or liver cells, and in striated cardiac and skeletal muscle cells. Through its role in the glucose-alanine cycle, ALT enables efficient muscle contraction by using muscle proteins to produce glucose and dispose of wastes through the liver.
Both human and veterinary health professionals commonly measure ALT in blood test panels. Elevated ALT levels in the blood are a sign of hepatocellular damage or liver cell damage. When liver cells are damaged, ALT effectively ‘leaks’ from those cells, causing it to appear in higher concentrations in the blood panels. ALT is therefore known as a scattering enzyme. It is often measured in combination with aspartate transaminase (AST), alkaline phosphatase, and bilirubin to evaluate for liver disease.
Some common causes of elevated alanine aminotransferase include liver disease such as cirrhosis, viral hepatitis, liver tumors, and ischemia or lack of blood flow to the liver. Additional causes of elevated ALT include drugs that affect the liver such as statins, some antibiotics, chemotherapy, aspirin, narcotics, and barbiturates.
ALT can also be elevated in other diseases such as pancreatitis, mononucleosis or celiac disease. Sometimes, ALT levels are elevated due to a recent cardiac catheterization or surgery. Individuals on long-term medications or those who have risk factors for liver disease are often monitored regularly for high ALT levels.
A normal range of ALT resulting from an alanine aminotransferase test for an adult human is 0-40 units/liter. The ranges can vary, however, according to the sexes and even the animal species. Test results can also vary from one test lab to another.
The results of the alanine aminotransferase test can also be skewed by cigarette smoking, medications, or pregnancy. Sometimes, performing strenuous exercise immediately before the test can skew your results. Some herbs, such as echinacea or valerian, are also able to raise ALT levels in the blood.
