The liver filters the blood to remove waste, process drugs, store blood sugar, regulate clotting and produce proteins that act as enzymes – substances that initiate reactions in the body. Liver damage caused by inflammation, infection or blockage allows increased levels of enzymes to leak into the blood. The formation of a tumor – an abnormal growth of cells – in the liver, a condition known as liver cancer, damages the surrounding healthy cells. Therefore, liver cancer may cause elevated liver enzymes.
Although less common in the United States, liver cancer remains one of the most common types of cancer worldwide, according to the MayoClinic website. Because the early stages of liver cancer fail to produce any physical symptoms, a blood test, known as a liver function test, determines the amount of four different enzymes present in the blood. Increased amounts of any or all of these enzymes may indicate the presence of liver damage that may be due to liver cancer.
Although the liver produces many different proteins, liver function tests provide information on four main liver enzymes: alkaline phosphatase or ALP, alanine aminotransferase or ALT, aspartate aminotransferase or AST and lactate dehydrogenase or LDH. The amount of these enzymes can help doctors determine the presence of liver damage. Comparing the amounts of each, such as directly comparing AST to ALT can help doctors distinguish between the causes of damage that assists the detection of liver cancer, according to Lab Tests Online.
High Enzyme Levels
Because the cells that form the bile ducts – the tubes that connect the liver, gall bladder and intestines – contain higher amounts of ALP, a liver tumor that blocks bile ducts causes a significant increase in the amount of ALP in the blood, according to Lab Tests Online.
Moderate Enzyme Increases
Some tumors of the liver may cause only moderate increases in one or more of the liver enzymes. Liver function tests that reveal moderate increases in ALT and AST can indicate cirrhosis of the liver – a condition characterized by the formation of scar tissue due to damage caused by inflammation. In addition, some liver cancers produce a moderate increase in ALT and AST levels.
The symptoms caused by liver cancer are often non-specific, making diagnosis difficult. Patients with liver cancer may experience unexplained weight loss due to the liver failing to produce enough bile – a digestive substance necessary for fat breakdown and absorption. The weight loss may also be accompanied by nausea, vomiting and a lack of appetite. Other symptoms include upper abdominal pain with abdominal swelling, weakness, fatigue and an enlarged liver. Because the liver filters out bilirubin – a waste product from the breakdown of red blood cells, a loss of this function due to damage may cause jaundice that causes a yellow discoloration of the skin and whites of the eyes. These symptoms along with knowing the levels of certain liver enzymes can help doctors diagnose or rule out liver cancer.