Liver enzymes Albumin is a protein made by the liver, and can be measured very easily. It is the main constituent of total protein; the remaining fraction is called globulin. Albumin levels are decreased in chronic liver disease, such as cirrhosis. It is also decreased in nephrotic syndrome, where it is lost through the urine. Poor nutrition or protein catabolism may also lead to hypoalbuminaemia. The half-life of albumin is about 20 days. Albumin is not considered to be a very useful marker of liver synthetic function; coagulation factors are much more sensitive.
Alanine transaminase (ALT), also called serum glutamic pyruvate or even alanine aminotransferase is an enzyme present in liver cells. When a cell is damaged, it leaks this enzyme into the blood, where it is measured. ALT rises up dramatically in small liver damage, such as the following: Paracetamol, vital overdose. It is measured in multiples of the upper limit of normal (ULN).
Aspartate transaminase (AST), also called serum glutamic oxaloacetic transaminase is another enzyme found in the liver, but is also present in red cells, and cardiac and skeletal muscle and is therefore not specific to the liver. Therefore, the ratio of AST to ALT is sometimes useful in differentiating between causes of liver damage.
Alkaline phosphatase (ALP) is an enzyme in the cells lining the biliary tract of the liver. ALP levels in plasma will rise with large bile tract obstruction, cholestasis or infiltrative diseases of the liver. ALP is also present in bones and placenta tissue, so it is higher in growing children and elderly patients.
Total bilirubin (TBIL) || Bilirubin is a breakdown product of heme (a part of haemoglobin in red blood cells). The liver is responsible for clearing the blood of bilirubin. It does this by the following mechanism: bilirubin is taken up into hepatocytes, conjugated (modified to make it water-soluble), and secreted into the bile, which is excreted into the intestine.
Increased total bilirubin causes jaundice, and can signal a number of problems such as the following: Prehepatic: Increased bilirubin, This can be due to a number of causes, including hemolytic anemias and internal hemorrhage. Hepatic: Problems with the liver, which are reflected as deficiencies in bilirubin. Metabolism reduced, impaired conjugation of bilirubin, and reduced hepatocyte secretion of bilirubi. Some examples would be cirrhosis and viral hepatitis. Posthepatic: Obstruction of the bile ducts.
It is very important to normalize the INR before operating on people with liver problems (usually by transfusion with blood plasma containing the deficient factors) as they could bleed excessively.