According to the American Academy of Family Physicians, your health care provider might ask you to have blood tests often referred to in aggregate as liver function tests, or LFTs. Normally, liver enzymes or proteins are only present in your liver. However, if your liver has been damaged by disease or injury, the enzymes can be found in your blood. The tests measure the amount of enzymes present, which represents liver damage - not the health of your liver. The results assist your health care provider to determine the type of injury or disease and its status.
Aminotransferases
This group of liver enzymes includes aspartate aminotransferase known as AST or SGOT and alanine aminotransferase abbreviated as ALT or SGPT. The enzyme AST or SGOT is found in your liver but is also found in your heart, kidney and brain. If your AST level is increased, it means there was damage to one of these organs. Because AST is found in multiple organs it is a less specific test of how your liver is functioning.
ALT is an enzyme predominantly found in your liver. If your ALT blood level is elevated it is a better measurement of how your liver is functioning. If it is elevated it means that your liver has suffered some type of injury, damage or disease. Both ALT and AST levels can be elevated in chronic alcohol abuse, Hepatitis B and C, drug use, presence of liver tumors, iron or copper deficiency and muscle injury.
Gamma-glutamyltransferase
If you have a blockage in a bile duct your liver enzyme Gamma-glutamyltransferase, or GGT level may be elevated. GGT can also be high if you have liver disease, which prevents your liver from producing bile. Drinking more than three alcoholic drinks per day can also raise your GGT level. In addition, medications including Phenobarbital and phenytoin, brand name Dilantin can increase the level of this liver enzyme. If you take these medications, an elevated GGT level does not mean that you have liver disease.
Lactate dehydrogenase
Lactate dehydrogenase or LDH is another important liver enzyme. While it is not as good as AST and ALT at pinpointing liver disease or damage, it is very accurate when it comes to identifying ischemic liver injury. This means that if your liver suffered an injury that robbed it of the nutrients needed to live, an elevated LDH level would signal ischemic, or tissue death injury of your liver.
