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Hepatocellular injury from viral hepatitis, alcoholic liver disease, drug toxicity (acetaminophen, statins), or autoimmune causes hepatocyte necrosis and inflammation. Elevated transaminases (ALT > AST in viral/drug injury; AST > ALT in alcoholic hepatitis) indicate ongoing hepatocyte injury. Synthetic dysfunction (elevated INR, low albumin, prolonged PT) indicates loss of hepatocyte mass or function and predicts poor prognosis. Acute hepatic failure from massive necrosis causes metabolic encephalopathy, coagulopathy, and hemodynamic collapse. Chronic injury leads to fibrosis and cirrhosis.
Distinguish acute hepatocellular injury (elevated transaminases, normal or mildly elevated bilirubin, preserved synthetic function) from acute liver failure (coagulopathy, encephalopathy, jaundice developing rapidly). Study the pattern of enzyme elevation: marked ALT elevation (>10x) suggests viral or drug-induced injury.
Elevated transaminases do not always indicate hepatocellular necrosis; some elevation occurs with cholestasis or cirrhosis from hepatocyte inflammation. The INR and albumin are better markers of synthetic function than transaminase levels. Some ALT/AST elevation in viral hepatitis is normal—the degree correlates poorly with disease severity.
The liver is uniquely vulnerable to injury because of its dual blood supply and metabolic centrality — it processes everything absorbed from the gut, detoxifies drugs and metabolic waste, and synthesizes most of the proteins the body depends on. When hepatocytes are damaged, they release intracellular enzymes into the bloodstream, providing measurable biomarkers of ongoing injury. Understanding which enzymes rise, in what ratio, and what that predicts about the nature and severity of injury is the foundation of liver disease assessment.
The key injury markers are the transaminases: alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Both catalyze amino acid metabolism and are concentrated inside hepatocytes. When cells die or their membranes are disrupted, these enzymes leak into blood. ALT is highly liver-specific; AST is also found in cardiac and skeletal muscle, so isolated AST elevation may reflect muscle injury rather than liver disease. The AST:ALT ratio is diagnostically informative: a ratio greater than 2:1 strongly suggests alcoholic hepatitis (alcohol preferentially damages the mitochondria where AST is stored, and alcohol also depletes pyridoxal phosphate needed for ALT synthesis). Viral hepatitis and drug-induced liver injury typically produce the opposite pattern — ALT dominates, and elevations can exceed 10–50 times the upper limit of normal in acute presentations.
Critically, transaminase levels measure cell death, not liver function. A liver can have modestly elevated transaminases while still performing its synthetic tasks perfectly well. To assess whether the liver is actually failing — losing its ability to do what only it can do — you measure synthetic markers: the prothrombin time (PT/INR) and albumin. The liver synthesizes all clotting factors except factor VIII; when hepatocyte mass falls or function degrades, factor production drops, and the PT lengthens. Albumin, the major plasma protein responsible for maintaining oncotic pressure and transporting drugs and hormones, has a half-life of about 20 days — so falling albumin reflects sustained synthetic failure over weeks, whereas PT can rise within hours of acute massive injury.
This distinction has enormous prognostic weight. Acute liver failure — the most dangerous presentation — is defined not merely by high transaminases but by coagulopathy (elevated INR) plus encephalopathy developing within weeks of jaundice onset. The hepatic encephalopathy reflects failure of the liver's detoxification function: ammonia and other nitrogenous compounds, normally cleared by the liver, accumulate in blood and cross the blood-brain barrier, causing confusion, asterixis, and eventually coma. The coagulopathy creates bleeding risk at every site. Together, acute liver failure has very high short-term mortality without transplantation, while someone with viral hepatitis causing transaminases 30× normal but normal INR and albumin will generally recover fully with supportive care. Learning to read the liver panel means distinguishing injury (transaminases) from failure (INR, albumin, encephalopathy) — and recognizing that the latter is what determines the prognosis.