It is used often times to confirm that the alkaline phosphatase is of the hepatic etiology. Certain GGT levels, as an isolated finding, reflect rare forms of liver disease. Medications commonly cause GGT to be elevated. Hemoglobin is derived from red cells that have outlived their natural life and subsequently have been removed by the spleen. Hemoglobin is transferred to the liver where it undergoes further metabolism in a process called conjugation.
Conjugation allows hemoglobin to become more water-soluble.
The water solubility of bilirubin allows the bilirubin to be excreted into bile. Bile then is used to digest food. As the liver becomes irritated, the total bilirubin may rise. These two components are called total bilirubin and direct bilirubin. The direct bilirubin fraction is that portion of bilirubin that has undergone metabolism by the liver.