Alanine Aminotransferase, known as ALT, is an enzyme frequently measured in routine blood tests. It was previously known as SGPT (Serum Glutamic Pyruvic Transaminase). Understanding this marker provides insights into bodily functions. This article clarifies what ALT (SGPT) is and what its levels indicate.
Understanding ALT (SGPT)
ALT is an enzyme that plays a role in metabolism, converting alanine and alpha-ketoglutarate into pyruvate and glutamate. This process is significant for energy production and amino acid metabolism within cells. While found in smaller amounts in the kidneys, heart, and muscles, ALT’s highest concentration is within liver cells.
A small amount of ALT naturally circulates in the bloodstream. When liver cells are damaged, they release larger quantities of this enzyme into the blood, leading to elevated levels. The standard unit for measuring enzyme activity is International Units per Liter (IU/L), quantifying the amount of enzyme in a given volume of blood.
Why ALT (SGPT) Levels are Tested
Doctors frequently order ALT tests to assess liver health, as elevated levels signal damage to liver cells. When liver cells are injured, their membranes become permeable, allowing ALT to leak into the bloodstream. This leakage provides an early indication of liver issues.
The ALT test is often part of a comprehensive metabolic panel or liver function test, used for screening liver conditions. It also helps in monitoring the progression of existing liver diseases, such as hepatitis or cirrhosis. The test also evaluates the impact of certain medications known to affect liver function, enabling healthcare providers to adjust treatments.
Common Causes of Elevated ALT (SGPT)
Elevated ALT levels stem from common conditions affecting the liver. Non-alcoholic fatty liver disease (NAFLD), where excess fat accumulates in the liver, is a frequent cause of mild to moderate ALT elevation. Alcoholic liver disease, from excessive alcohol consumption, also commonly leads to increased ALT due to liver cell damage. Various forms of hepatitis, including viral (like hepatitis B and C) and autoimmune, cause inflammation and destruction of liver cells, resulting in significantly high ALT levels.
Certain medications, such as statins or acetaminophen in large doses, can temporarily elevate ALT. Less common causes include liver cirrhosis, involving extensive scarring, or strenuous physical exercise or muscle injury, which can cause a slight, transient rise in ALT due to its presence in muscle tissue.
Interpreting Your ALT (SGPT) Results
A “normal” ALT level generally falls below 40-50 IU/L for adults, though specific ranges can vary between different laboratories. Mild elevations, up to twice the upper limit of normal, might suggest conditions like fatty liver or medication side effects. Moderate elevations, two to five times the normal limit, could indicate ongoing inflammation or early liver disease. Severely elevated ALT levels, exceeding ten times the normal range, typically point to acute liver damage, such as severe viral hepatitis or drug-induced liver injury.
An elevated ALT level is an indicator, not a definitive diagnosis. Further diagnostic tests, such as additional blood work, imaging studies, or a liver biopsy, are usually required to pinpoint the underlying cause. Always consult a healthcare provider for a personalized interpretation of your ALT results and to discuss next steps.