Decreased activity of commonly measured serum enzymes: causes and clinical significance.

The clinical significance of decreased enzyme activity in serum is less well understood than is the significance of increased activity. This review updates the causes and possible clinical significance of decreased activity in serum of the commonly measured enzymes: alkaline phosphatase, creatine kinase, aspartate and alanine aminotransferases, amylase, lactic dehydrogenase, and gamma-glutamyltranspeptidase.