Alkaline phosphatase

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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AP; Phosphatase, alkaline

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Enzyme group belonging to the hydrolases, which cleaves the esterified phosphoric acid from nucleotides, phosphatides and sugar phosphoric acids. Alkaline phosphatases are active in an alkaline environment. The total serum and plasma activity of alkaline phosphatases is the sum of the individual activities of 17 different phosphatases. isoenzymes (e.g. liver-AP, bone-AP, placentza-AP, small intestine-AP).

General information
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The different forms of AP are encoded by 4 genes. Three genes encode the tissue-specific isoenzymes small intestinal AP, placental AP and germ cell AP, the fourth gene encodes the tissue-unspecific isoenzyme, which is mainly found in the liver, bones and kidneys. Posttranslational modifications result in liver-AP, bone-AP and kidney-AP. The activity in normal serum is mainly due to the liver and bone enzyme.

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Standard values:

  • Women: 35 - 104 U/l
  • Men: 40 - 129 U/l
  • Children and adolescents: physiologically significantly higher and age-dependent (30-390 U/l).

Pathologically elevated: Hodgkin's disease, renal cell carcinoma, paraneoplastic in a bronchial carcinoma, acromegaly, rickets, cholestasis (together with bilirubin, GGT, cholestasis parameters), hepatic cell necrosis parameters (together with GOT, GPT, GLDH) Osteomalacia, Paget's disease, hyperparathyroidism, bone tumors, bone metastases

False high values: drugs (allopurinol, carbamzepine, cotrimoxazole, cyclophosphamide, erythromycin, gold preparations, oxacillin, methotrexate, oxacillin, rifampicin, sulfasalazine).

Pathologically decreased: vitamin D intoxication, pernicious anemia, hypothyroidism, malassimilation. Wilson's disease, protein deficiency (liver cirrhosis, nephrotic syndrome)

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Neumeister B (2018) Thyroid hormones. In: Neumeister B et al. (Eds) Clinical guide to laboratory diagnostics. Elsevier GmbH S. 87-89


Last updated on: 29.10.2020