is an enzyme which catalyzes the hydrolysis of phosphate monoesters. It is membrane-bound widely found: liver - 55...
- is an enzyme which catalyzes the hydrolysis of phosphate monoesters.
- It is membrane-bound
- widely found:
- liver - 55%; in hepatocytes next to biliary canaliculi
- bone - 45%; in osteoblasts
- gut - 5%
- kidney
- placenta
- The liver, bone and kidney enzymes are different forms of the same gene product; the gut and placental forms are isoenzymes.
- Gut ALP rises after meals
- Bone ALP increases at the time of physiological growth spurts.
- Placental ALP normally increases at the end of the third trimester.
Increased levels of plasma alkaline phosphatase include:
- hepatobiliary disease including:
- Cholestasis ( increase 10 times normal levels )
- hepatocyte disease-viral hepatitis
- 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
Reduced alkaline phosphatase
- zinc deficiency
- magnesium deficiency
- hypophosphatasia
- cardiac surgery and cardiopulmonary bypass
- artifacts associated with collection of blood in EDTA or oxalate anticoagulant
- hypothyroidism
- severe anaemia
- pernicious anaemia (in pernicious anaemia, osteoblast activity is dependent on cobalamin, and bone metabolism is affected by deficiency of cobalamin)
- protein/calorie deficiency
- oestrogen replacement therapy in postmenopausal women
- end-stage osteopaenia of chronic renal osteodystrophy
- Wilson's disease
- achondroplasia and hypothyroidism in children
- vitamin C deficiency
- 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
