Serum Glutamic Pyruvic Transaminase (SGPT) is an enzyme measurement frequently seen on blood test reports, often as part of a routine liver function panel. It is now more commonly referred to as Alanine Aminotransferase (ALT). The test quantifies the amount of this enzyme circulating in the bloodstream, providing a sensitive indicator of liver health. Elevated levels signal that liver cells may be experiencing stress or damage.
The Role and Function of SGPT (ALT)
SGPT (ALT) is an intracellular enzyme that primarily resides within the liver’s main functional units, the hepatocytes. Although smaller quantities are found in the kidneys, heart, and skeletal muscle, its high concentration in the liver makes it a specific marker for hepatic injury. The enzyme plays a role in the body’s metabolism by processing amino acids.
Its function involves transamination, catalyzing the transfer of an amino group from the amino acid alanine to alpha-ketoglutarate. This reaction produces pyruvate and glutamate, which are used for energy production or other metabolic pathways. In a healthy liver, hepatocyte membranes contain the enzyme, resulting in only trace amounts in the blood. When liver cells are damaged, their membranes become compromised, allowing the enzyme to leak out and elevate blood SGPT levels.
Interpreting Normal and Elevated Levels
Normal SGPT levels are low, ranging between 7 and 56 Units per Liter (U/L) of blood, though this reference range varies between laboratories. For adult males, the normal range is often 10 to 40 U/L, and for adult females, 7 to 35 U/L. A value within this expected range suggests the liver is functioning normally with minimal cellular injury.
An elevation in SGPT is a direct indication of liver cell damage, as the enzyme has escaped the cell and entered the circulation. A mild increase, slightly above the upper limit, may suggest mild liver stress, such as early-stage fatty liver disease or medication side effects. Conversely, a significantly elevated SGPT level, potentially reaching hundreds of U/L, suggests acute and severe liver inflammation or injury. These higher numbers are commonly seen in conditions like acute viral hepatitis or severe drug-induced liver damage. The degree of elevation helps gauge the severity of the issue but does not specify the exact cause, requiring further investigation.
Key Factors That Cause SGPT Elevation
One common reason for chronically elevated SGPT is Non-Alcoholic Fatty Liver Disease (NAFLD), now often called Metabolic Dysfunction-Associated Steatotic Liver Disease. This condition involves excess fat accumulation within liver cells, linked to obesity, type 2 diabetes, and high cholesterol. The fat buildup causes inflammation and stress on the hepatocytes, leading to the gradual leakage of ALT into the bloodstream.
Excessive alcohol consumption also results in significant SGPT elevation due to the direct toxic effects on liver cells. This leads to alcoholic liver disease, ranging from simple fatty liver to severe alcoholic hepatitis and cirrhosis. Certain medications are another frequent cause of liver injury, known as drug-induced hepatotoxicity. Common culprits include acetaminophen, certain antibiotics, and cholesterol-lowering statin drugs.
Viral infections, specifically Hepatitis A, B, and C, induce acute or chronic inflammation that destroys liver cells and causes a spike in SGPT levels. Less common factors include autoimmune hepatitis, where the immune system attacks liver cells, and hemochromatosis, which causes iron overload. Even intense physical exertion or muscle injury can cause a temporary, mild rise in SGPT unrelated to liver disease.