Serum Alkaline Phosphatase

Background

  • 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

Indications

  • Evaluation of Liver Function: alkaline phosphatase is a standard component of liver function tests (LFT’s)

  • xxx


Etiology of Elevated Alkaline Phosphatase (see Elevated Liver Function Tests, [[Elevated Liver Function Tests]])

Moderate Alkaline Phosphatase Elevation (<4x Upper Limit of Normal)

Hepatic

Non-Hepatic

  • Benign Familial Elevation of Alkaline Phosphatase
    • Physiology: intestinal source
  • High Bone Turnover
  • Influx of Intestinal Alkaline Phosphatase After Eating a Fatty Meal
    • Epidemiology: occurs in patients with blood type O or B
  • Malignancy
  • Physiologic Elevation of Alkaline Phosphatase: occurs in children and adolescents
  • Third Trimester of Pregnancy (see Pregnancy, [[Pregnancy]])
  • Other

Marked Alkaline Phosphatase Elevation (≥4x Upper Limit of Normal)

Intrahepatic Cholestasis

Extrahepatic Cholestasis (Biliary Obstruction)

  • Acute Pancreatitis (see xxxx, [[xxxx]])
    • Physiology: xxx
  • Biliary Infection
  • Biliary Stricture
    • Chronic Pancreatitis with Stricture of Distal Bile Duct (see Chronic Pancreatitis, [[Chronic Pancreatitis]])
    • Post-Liver Transplant Biliary Anastomotic Stricture (see Liver Transplant, [[Liver Transplant]])
    • Post-Procedure
    • Primary Sclerosing Cholangitis (PSC) with Extrahepatic Bile Duct Stricture (see Primary Sclerosing Cholangitis, [[Primary Sclerosing Cholangitis]])
  • Choledocholithiasis (see Cholelithiasis, [[Cholelithiasis]])
    • Epidemiology: most common etiology of extrahepatic biliary obstruction
  • Malignant Biliary Obstruction

Non-Hepatic

  • Transient Hyperphosphatemia of Infancy and Childhood

References

  • Heat stability of human serum alkaline phosphatase in bone and liver diseases. Clin Chim Acta. 1972 Oct;41:329-34 [MEDLINE]