Alkaline phosphatase is an enzyme that catalyzes the hydrolysis of organic monophosphates. It is called alkaline phosphatase because its optimal pH is 8.6-10.3. This enzyme is widely present in human tissues and body fluids, with bone, liver, placenta and kidney being the main ones. When lesions occur in these tissues and organs, it can lead to high serum alkaline phosphatase. In addition, it can also be seen in physiological elevations. Clinically common elevations of serum alkaline phosphatase are mainly in the following cases: i. Physiological elevations: children and adolescents whose bones are growing and developing, as well as women during pregnancy, such as the development of the placenta and fetal bones, perform liver biochemical tests and only this enzyme is elevated in the blood, it should be noted that it may be physiologically elevated. Elevation of alkaline phosphatase can also occur after eating foods with high fat content or after taking certain drugs, such as estrogen and progestin. Pathological elevation: 1. Skeletal disease: When deformational osteitis, bone injury, bone disease, such as rickets, osteochondrosis, osteogenesis imperfecta, osteoblastoma, fracture recovery, etc., alkaline phosphatase in osteoblasts can be released into the blood, resulting in an increase in their serum levels. During biochemical examination, only this enzyme is usually elevated, while others, such as glutamate aminotransferase (ALT), glutathione aminotransferase (AST) and glutamyl transpeptidase (GGT), are not elevated; 2. Liver and biliary diseases: alkaline phosphatase exists in the hepatocytes that constitute the epithelium of the capillary bile ducts, and if the damage to the hepatocytes is dominated by damage to the capillary bile ducts, the enzyme can be prominently elevated, often accompanied by elevated GGT, ALT and AST The elevation is not obvious. For example, various causes of intrahepatic cholestasis and liver damage are common, such as drug-related liver damage, primary biliary cholangitis, hepatocellular carcinoma, and intrahepatic metastatic carcinoma. In addition, when the bile duct is obstructed, the enzyme cannot be excreted normally through the bile duct, which can also cause its significant elevation, accompanied by an increase in GGT, and an insignificant increase in ALT and AST. Common diseases are bile duct stones, bile duct cancer, bile duct stricture, IgG4-associated cholangitis, primary sclerosing cholangitis, and pancreatic head cancer. The enzyme can also be elevated in liver damage with predominantly damaged hepatocytes, but it is not obvious, and the prominent ones are elevated ALT and AST. For example, viral hepatitis, drug-related liver damage, autoimmune hepatitis, alcoholic liver damage, etc.; 3. Other: rare conditions such as kidney disease, anemia, leukemia, etc. can also cause elevation of this enzyme. If serum alkaline phosphatase is elevated without associated physiological causes, further examination is needed to identify the cause and take targeted therapeutic measures.