Which single enzyme is commonly used as a marker of hepatic injury?

• A. AST
• B. Bilirubin
• C. Albumin
• D. Ammonia

Answer: (A)

Enzymes that leak into the blood when liver cells are damaged serve as markers of hepatic injury. Aspartate aminotransferase is commonly measured because it is present in high amounts in hepatocytes and is released into the bloodstream when those cells are injured. This makes it a sensitive indicator of hepatocellular injury, so it’s frequently used in liver injury testing. It’s worth noting that this enzyme isn’t exclusive to the liver; it’s also found in heart and muscle, which is why elevations can occur with non-liver tissue injury as well. The other options are not enzymes that reflect hepatocellular injury: bilirubin is a pigment indicating bile flow and excretion status, albumin reflects the liver’s synthetic function, and ammonia reflects metabolic detoxification capacity.