Question

Which of the following enzymes are indicators of liver dysfunction?

• A. ALT
• B. GGT
• C. ALP
• D. All of the above

Answer 1

Answer:

D. All of the above

Liver Function Tests (LFTs) and Key Enzymes

• Alanine Aminotransferase (ALT): Often referred to as SGPT (Serum Glutamic-Pyruvic Transaminase), this is the most specific enzyme for hepatocellular injury. It is found primarily in the liver. Significant elevations usually indicate viral hepatitis, alcohol abuse, or drug-induced liver injury.
• Aspartate Aminotransferase (AST): Also known as SGOT (Serum Glutamic-Oxaloacetic Transaminase). While less specific than ALT, it is present in the liver, heart, skeletal muscle, and kidneys. An AST:ALT ratio is frequently calculated to distinguish between alcoholic liver disease (where AST is typically twice the level of ALT) and other liver conditions.
• Alkaline Phosphatase (ALP): This enzyme is found in the liver, bile ducts, and bone. Elevated levels combined with increased GGT typically point towards cholestasis (bile duct obstruction or bile flow issues) rather than direct liver cell damage.
• Gamma-Glutamyl Transferase (GGT): A highly sensitive marker for alcohol-related liver damage and bile duct disease. It is often used to confirm that an elevated ALP level is of liver origin rather than bone origin.
• Lactate Dehydrogenase (LDH): A non-specific marker found in almost all body tissues. While it can be elevated in severe liver disease, its lack of specificity makes it less reliable for diagnosing liver dysfunction compared to ALT or AST.

Clinical Significance for Exams

1. Hepatocellular Pattern: Marked by disproportionate elevation of ALT and AST. Common in acute hepatitis.
2. Cholestatic Pattern: Characterized by a predominant rise in ALP and bilirubin. Common in gallstones, bile duct tumors, or primary biliary cholangitis.
3. Reference Ranges: Candidates should note that specific reference ranges vary by laboratory and methodology, but diagnostic focus remains on the pattern of enzyme elevation.