Albumin is a protein that circulates in the blood and is exclusively produced by the liver. It is the primary constituent of total protein, the other being globulins. In chronic liver diseases such as liver cirrhosis, the levels of albumin get reduced. Hypoalbuminaemia also occurs in nephrotic syndrome when albumin is lost through the urine. There can be numerous reasons for abnormal levels of albumin, which is why this test is not regarded as a very useful indicator of liver synthetic function.

Serum Glutamic Pyruvate Transaminase (SGPT) or ALT is an enzyme which is found almost exclusively in the liver cells. Its presence in blood is an indication of liver cell damage. ALT leakage into the blood is also seen in acute liver damage conditions caused by viral hepatitis or paracetamol overdose.

Sometimes called Glutamic Oxaloacetic Transaminase (SGOT), AST is an enzyme related to the liver. However, it is not exclusively produced in the liver and can also be found in the cardiac and the skeletal muscles besides a number of other tissues. Although elevated levels of AST may indicate a disorder, but whether the condition is associated with the liver or not remains somewhat unclear. Therefore, a ratio of the AST to the ALT is helpful to distinguish the sources of liver damage.

It is an enzyme found in the cells of the biliary ducts in the liver. When there is an obstruction in the bile-duct, intrahepatic cholestasis or liver infiltrative diseases, the ALP levels in the plasma shoot up. Since ALP is also found in bone and placental tissues, ALP content is higher in growing children or adults suffering from the Paget’s disease.

Bilirubin is a breakdown product of heme catabolism. It is the function of the liver to process bilirubin so that it can be excreted out of the body. Bilirubin is first made water soluble in the hepatocytes and is then secreted into the bile which subsequently goes into the intestines. Abnormal levels of bilirubin can indicate liver dysfunction, gall bladder dysfunction or other bile related disorder.

Normal levels of conjugated bilirubin in the blood are an indication that unconjugated bilirubin is present in excess, which may furthermore indicate Hemolysis, cirrhosis or viral hepatitis. However, if the levels of direct bilirubin are increased, it can be said that the liver is able to conjugate the bilirubin but is unable to excrete it, which may furthermore be an indication of gallstones or cancer.

GGT is quite specific to the liver and a more sensitive indicator of cholestatic damage as compared to ALP. However, even sub clinical levels of liver dysfunction may elevate the level of GGT. Increased GGT in the blood could be due to dysfunction in the liver, gallbladder, or the tubes connecting them.