serumALT

Serum ALT, or alanine aminotransferase, is an enzyme primarily found in liver cells. It participates in amino acid metabolism by transferring an amino group from alanine to an acceptor such as alpha-ketoglutarate, producing pyruvate and glutamate. When hepatocytes are damaged or inflamed, ALT leaks into the bloodstream, causing elevated serum levels. Because of its relatively liver-specific distribution, Serum ALT is widely used as a marker of hepatocellular injury.

Normal reference ranges for ALT vary by laboratory, assay, age, and sex, but in adults the upper limit is typically around 7 to 56 units per liter (U/L). Pediatric ranges differ, and results should be interpreted in the context of the specific reference interval provided by the testing laboratory. Elevation magnitude can reflect the extent of liver injury but is not specific to a particular disease.

Elevated serum ALT indicates hepatocellular injury but does not identify the cause. Common etiologies include acute or chronic viral hepatitis, nonalcoholic fatty liver disease, alcoholic liver disease, drug- or toxin-induced liver injury, autoimmune hepatitis, and ischemic or congestive conditions affecting the liver. ALT may be raised in a variety of conditions, whereas cholestasis tends to elevate alkaline phosphatase and gamma-glutamyl transferase more markedly. The ratio of AST to ALT can offer clues in some contexts, with alcohol-related liver disease often showing a higher AST relative to ALT.

ALT testing is used to screen for and monitor liver disease, evaluate unexplained abdominal symptoms, and assess liver injury in patients taking potentially hepatotoxic medications. Limitations include its lack of specificity for the underlying diagnosis and its variable levels among individuals and laboratories; interpretation should consider other liver tests and clinical context.