Alkaline phosphatase (ALP) is present as a number of isoenzymes and is found in the highest concentrations in bone, liver, kidney, intestine and placenta.
ALP is used for diagnosis and monitoring treatment of liver, bone, intestinal and parathyroid diseases. ALP elevations are highest in cholestatic disease, particularly with obstructive jaundice, and infiltrative disease whereas lower levels are seen in hepatocellular disease.
ALP also is elevated in disorders of the skeletal system that involve osteoblast hyperactivity and bone remodelling, such as Paget’s disease, hyperparathyroidism, rickets and osteomalacia, fractures, and malignant tumours. Increased ALP activity sometimes is observed in children caused by increased osteoblast activity following accelerated bone growth.