Overview
Serum Alanine Transferase, commonly known as ALT or SGPT, is an enzyme found predominantly in the liver and plays a key role in amino acid metabolism. It catalyzes the transfer of an amino group from L-alanine to α-ketoglutarate, producing pyruvate and L-glutamate, with pyridoxal-5-phosphate acting as a cofactor. ALT is mainly located in the cytoplasm of hepatocytes, and its activity in liver tissue is significantly higher than in serum. When liver cells are damaged, ALT is released into the bloodstream, making it a sensitive marker of hepatocellular injury. ALT estimation is usually performed along with other liver function tests such as AST, ALP, and bilirubin to diagnose and monitor liver diseases.
Symptoms
Raised ALT levels are often associated with symptoms of liver damage, though elevations may occur before symptoms appear. Common symptoms include nausea, vomiting, loss of appetite, fatigue, weakness, jaundice with yellowing of the skin and eyes, abdominal pain or swelling, swelling of ankles and legs, dark-colored urine, light-colored stools, and frequent itching. In some individuals, especially in early or mild liver disease, ALT may be elevated even in the absence of obvious clinical symptoms.
Causes
Elevated ALT levels are commonly caused by liver-related conditions such as viral hepatitis, alcoholic liver disease, non-alcoholic fatty liver disease, drug-induced liver injury, autoimmune hepatitis, ischemic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Certain medications, including antitubercular drugs, statins, and paracetamol, can increase ALT due to hepatocyte toxicity. ALT may also rise in muscle disorders, biliary disease, and systemic illnesses. Low ALT levels may be seen in vitamin B6 deficiency, advanced liver disease with hepatocyte loss, chronic kidney disease, malnutrition, pregnancy, aging, or certain malignancies.
Risk Factors
Risk factors for abnormal SGPT levels include alcohol abuse disorder, obesity, diabetes, metabolic syndrome, and a family history of liver disease. Exposure to hepatitis viruses, use of hepatotoxic medications, and fatty liver disease significantly increase the risk of ALT elevation. Poor nutrition, chronic illness, and conditions affecting vitamin B6 status also influence SGPT activity. Improper sample handling, hemolysis, strenuous exercise, or intramuscular injections before testing may falsely alter ALT values.
Prevention
Prevention for SGPT abnormalities focuses on protecting liver health and early detection of liver injury. Avoiding excessive alcohol intake, maintaining a healthy diet, and controlling metabolic risk factors such as obesity and diabetes help reduce liver damage. Judicious use of medications known to affect the liver and regular monitoring in high-risk individuals support early intervention. Proper patient preparation before testing, timely sample processing, and interpretation alongside other liver function parameters help prevent misdiagnosis and ensure accurate assessment of liver status.
