AST and ALT belong to which category in liver function testing?

• A. Hepatocellular
• B. Hepatobiliary
• C. Synthetic
• D. Detoxification

Answer: (A)

AST and ALT are enzymes inside liver cells that spill into the bloodstream when those cells are damaged. This pattern of elevated transaminases signals hepatocellular injury, meaning injury to the liver cells themselves, rather than problems outside the liver or with the liver’s other functions. ALT is highly liver-specific, so its rise strongly points to liver involvement, while AST is also present in heart and muscle, which is why its elevation alone is less specific but still reflective of hepatocellular damage when considered with ALT. Other liver function markers—like alkaline phosphatase and GGT (hepatobiliary), or albumin and coagulation tests (synthetic function), or ammonia handling (detoxification)—reflect different aspects of liver physiology, not direct hepatocellular injury. Hence, AST and ALT are classic hepatocellular markers because their elevation directly indicates liver cell injury.