Tests that evaluate liver function include several enzymes found in the heart, skeletal muscle and red blood cells in addition to the liver. The greatest concentration of alanine aminotransferase, sometimes called ALT or sometimes SGPT and aspartate aminotransferase, also called AST or SGOT occurs in the liver. Damage to the liver cells causes ALT and AST to leak into the bloodstream. Normal levels of ALT range from 7 units to 56 units per liter, while normal levels of AST range from 5 units to 40 U/L, according to the Lab Tests Online website. Several types of liver disease cause elevated liver enzymes.
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A number of diseases can damage the liver, ranging from acute, temporary elevations to chronic mild elevation. Nonalcoholic fatty liver disease, commonly called NASH, mostly occurs as a result of overweight or diabetes. Nonalcoholic fatty liver disease, a chronic disease, affects 2 to 5 percent of Americans, mostly middle-aged, the National Institute of Diabetes and Digestive and Kidney Disorders website reports. Other medications such as cholesterol-lowering medications can also cause liver enzyme elevations. Acute hepatitis A, drug poisoning or overdose with acetaminophen can cause a sudden, very high increase in liver enzymes, more than 10 times the normal range, the Lab Tests Online website says.
Hepatitis B and C often cause chronic mild to moderate rises of up to four times the normal range. Alcoholic liver disease causes chronic elevations, with a AST/ALT ration greater than 1:1 often indicating alcoholic liver disease. Acute infections such as mononucleosis and cytomegalovirus can cause very high liver enzymes. Genetic disorders can also cause elevated liver enzymes.
A medical practitioner observes signs of a disease process. Signs that accompany elevated liver enzymes depend on the disease, but can include jaundice, a yellowish tinge to the skin and whites of the eyes, dark colored urine, clay-colored stools, fluid accumulation in the abdomen called ascites, intestinal bleeding, low-grade fever or weight loss. The liver and spleen may feel larger than normal.
People with elevated liver enzymes may not have any symptoms in the case of NASH, early alcoholic liver disease or chronic hepatitis B or C. If acute liver disease causes elevated liver enzymes, symptoms may include fatigue, nausea, vomiting, upper right quadrant abdominal pain and tenderness, loss of sex drive, mental changes or itching.