Liver Function Tests (LFT’s)

General Information

Specific Liver Function Tests (LFT’s)

Aminotransferases (see Serum Aminotransferases, [[Serum Aminotransferases]])

Alkaline Phosphatase (see Serum Alkaline Phosphatase, [[Serum Alkaline Phosphatase]])

  • Origin of Alkaline Phosphatase
    • Bone
    • Intestine
    • Kidney
    • Liver
    • Third Trimester Placenta
  • Determination of Origin
    • Elevated Alkaline Phosphatase Associated with a Normal Gamma-Glutamyl Transpeptidase or 5′-Nucleotidase Suggests a Non-Hepatic Source of the Alkaline Phosphatase
    • Fractionation of Alkaline Phosphatase: may also be used to determine origin
      • Heat-Labile Alkaline Phosphatase: suggests bone origin (“bone burns”)
      • Heat-Stable Alkaline Phosphatase: suggests liver origin
  • Alkaline Phosphatase Levels are Age-Dependent
    • Alkaline Phosphatase Levels are Higher (Up to 3x Adult Levels) in Children and Adolescents: due to physiologic osteoblastic activity
    • Normal Alkaline Phosphatase Level Increases from 40 to 65 y/o: especially in women

Bilirubin (see Serum Bilirubin, [[Serum Bilirubin]])

  • Bilirubin Species
    • Unconjugated (Indirect) Bilirubin (see Serum Bilirubin, [[Serum Bilirubin]])
    • Conjugated (Direct) Bilirubin (see Serum Bilirubin, [[Serum Bilirubin]])

Gamma-Glutamyl Transpeptidase (GGT) (see Serum Gamma-Glutamyl Transpeptidase, [[Serum Gamma-Glutamyl Transpeptidase]])

  • General Comments
    • Gamma-Glutamyl Transpeptidase is Elevated in Normal Neonates: levels decrease and reach adult levels by 5-7 mo of age
  • Origin of Gamma-Glutamyl Transpeptidase
    • Biliary Epithelial Cells
    • Brain
    • Heart
    • Hepatocytes
    • Kidney
    • Pancreas
    • Seminal Vesicle
    • Spleen

5′-Nucleotidase (see Serum 5′-Nucleotidase, [[Serum 5′-Nucleotidase]])

  • General Comments
    • Physiologic Function of 5′-Nucleotidase is Unknown
  • Origin of 5′-Nucleotidase
    • Blood Vessels
    • Brain
    • Endocrine Pancreas
    • Heart
    • Liver: liver is the only organ which releases 5′-nucleotidase into the serum

Lactate Dehydrogenase (LDH) (see Serum Lactate Dehydrogenase, [[Serum Lactate Dehydrogenase]])

  • General Comments
    • LDH is a Cytoplasmic Enzyme Found in Many Organs
    • There are 5 LDH Isoenzymes of LDH Present in the Serum: isoenzymes can be separated by electrophoresis
    • Slowest Migrating Isoenzyme is the Predominant Form Present in the Liver
  • Origin of Lactate Dehydrogenase Isoenzymes
    • LDH-1 (4H) Isoenzyme
      • Brain
      • Heart
      • Red Blood Cell (RBC)
    • LDH-2 (3H1M) Isoenzyme
      • Reticuloendothelial System
    • LDH-3 (2H2M) Isoenzyme
      • Lung
    • LDH-4 (1H3M) Isoenzyme
      • Kidney
      • Pancreas
      • Placenta
    • LDH-5 (4M) Isoenzyme
      • Liver
      • Striated Muscle


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