recent posts

Alkaline phosphatase (ALP)

Alkaline phosphatase (ALP)
  1. is an enzyme which catalyzes the hydrolysis of phosphate monoesters.
  2. It is membrane-bound
  3. widely found:
    • liver - 55%; in hepatocytes next to biliary canaliculi
    • bone - 45%; in osteoblasts
    • gut - 5%
    • kidney
    • placenta
  4. The liver, bone and kidney enzymes are different forms of the same gene product; the gut and placental forms are isoenzymes.
  5. Gut ALP rises after meals
  6. Bone ALP increases at the time of physiological growth spurts.
  7. Placental ALP normally increases at the end of the third trimester.

Increased levels of plasma alkaline phosphatase include:

  1. hepatobiliary disease including:
    • Cholestasis ( increase 10 times normal levels )
    • hepatocyte disease-viral hepatitis
  2. bone disease - increasedbone isoenzyme of alkaline phosphatase,
    • Paget's disease
    • osteomalacia and rickets
    • renal osteodystrophy
    • bone metastases
    • primary bone tumour e.g. sarcoma
    • recent fracture
    • growing child - especially at puberty
    malignancies resulting in expression of ALP-like gene e.g. seminomas

 

Reduced alkaline phosphatase

  1. zinc deficiency
  2. magnesium deficiency
  3. hypophosphatasia
  4. cardiac surgery and cardiopulmonary bypass
  5. artifacts associated with collection of blood in EDTA or oxalate anticoagulant
  6. hypothyroidism
  7. severe anaemia
  8. pernicious anaemia (in pernicious anaemia, osteoblast activity is dependent on cobalamin, and bone metabolism is affected by deficiency of cobalamin)
  9. protein/calorie deficiency
  10. oestrogen replacement therapy in postmenopausal women
  11. end-stage osteopaenia of chronic renal osteodystrophy
  12. Wilson's disease
  13. achondroplasia and hypothyroidism in children
  14. vitamin C deficiency
  15. other conditions that have suggested as possible causes of a low ALP include:
    • milk-alkali syndrome, excess ingestion of vitamin D, coeliac disease, hypoparathyroidism, intake of radioactive heavy metal, drugs such as clofibrate, recent massive blood transfusions, or posthepatic resection and transplantation
Alkaline phosphatase (ALP) Alkaline phosphatase (ALP) Reviewed by Radiology Madeeasy on August 31, 2010 Rating: 5
Powered by Blogger.