The liver undertakes a variety of functions, so liver function tests are done whether it is a normal physical examination or the diagnosis of related diseases. The functional damage of the liver is mainly manifested as changes in liver enzymatic changes, abnormal bilirubin metabolism, dysfunction of substance synthesis, decreased biodegradation function and other changes in four types of indicators, and biochemical abnormalities caused by different diseases, which have their own characteristics. In the face of multiple professional terms, ordinary people inevitably wonder, for example, how to interpret the relationship between test indicators and the nature and severity of the disease? Can a normal liver function test rule out the possibility of liver cancer? Let's explain the main points for you now.
To interpret the significance of liver function test indicators, it is first necessary to understand the functions of the liver. The liver is a labor-level organ in our body, which is responsible for synthesis, metabolism, bile secretion, phagocytosis, defense and other functions, and in the embryonic period, there are also hematopoietic functions. The first important function of the liver is the synthesis and metabolism of nutrients, involving sugar metabolism, protein synthesis and metabolism, fat metabolism, vitamin storage and metabolism, and hormone inactivation. The second item is bilirubin metabolism, where liver cells inside the liver produce bile acids and bile, which deliver 800 to 1,000 ml of bile to the gallbladder through the bile ducts every day. Item 3 is the detoxification function. The fourth item is immunity and defense function, the liver is actually the largest immune organ in the human body, with a strong reticuloendothelial cell phagocytic system. Item 5 is other functions, including regulating circulating blood volume, synthesizing coagulation factors, and participating in the regulation of water and electrolyte balance.
There are many indicators of liver function tests, and the laboratory test items can be divided into 4 categories, which reflect changes in liver cell damage, bilirubin metabolism, cholestasis, liver synthesis function and liver fibrosis. Category 1 is an indicator of hepatocyte damage, mainly including alanine aminotransferase ALT and agraviase AST, ALT is mainly distributed in the hepatocyte plasma, is a sensitive indicator of hepatocyte damage, AST is mainly distributed in hepatocyte mitochondria, representing the degree of hepatocyte damage. The ratio of these two indicators represents different disease states. For example, a sharp rise in ALT suggests acute or chronic viral hepatitis, and a mild rise suggests nonalcoholic steatohepatitis. A sharply elevated AST suggests primary biliary cholangitis or alcoholic liver disease, and abnormally elevated AST suggests a malignancy of the liver.
The second type of liver function test is bilirubin metabolism related indicators, mainly including total bilirubin TBIL, direct bilirubin DBIL, indirect bilirubin IBIL, serum bilirubin level and bile metabolism and excretion status related, liver failure, serum bilirubin level will appear significant, progressively elevated, and even the daily rise rate, more than 1 times more than the previous day, moreover, there will be bilirubin and ALT separation phenomenon. Elevated serum bilirubin levels can lead to jaundice, which, depending on changes in relevant indicators, helps to determine the type and cause of jaundice.
The third type of liver function test is cholestasis index, which mainly includes alkaline phosphatase ALP and γ-glutamyl transpeptidase GGT. Serum ALP mainly comes from the liver, bones, and intestines, and when the biliary tract is obstructed, ALP will be significantly increased, but the ATL level is not significantly elevated. It is worth noting that the change in ALP level is affected by a variety of factors, for example, after eating high-fat foods or pregnancy, ALP levels will be significantly elevated, so it is necessary to make a comprehensive judgment in combination with other test results. GGT is mainly distributed in the kidneys, liver, pancreas, the kidney release of GGT is mainly excreted through the urine, serum GGT mainly from the liver, bile duct epithelial cells and hepatocyte degeneration or necrosis, will lead to a large amount of GGT released into the blood, therefore, GGT levels are elevated, mainly suggest biliary tract diseases and liver diseases, such as gallstones or cholangitis, in addition, in acute hepatitis, GGT will appear mildly elevated, fatty liver or cirrhosis, GGT levels will also increase.
The fourth type of liver function test is an indicator of liver synthesis function, mainly including albumin AIb, prealbumin PA, prothrombin time PT, and cholinesterase CHE. The liver is the only organ that synthesizes albumin AIb, so changes in AIb levels the anabolic and reserve function of the liver can determine the severity of cirrhosis, and if this indicator continues to decline, it indicates an exacerbation of hepatocyte necrosis. Prealbumin PA, which can determine liver synthesis function and nutritional status. Prothrombin time PT reflects the degree of damage to liver cells, and when the damage is severe, the ability to synthesize coagulation factors decreases and the PT time is prolonged. Cholinesterase CHE, which reflects liver protein synthesis and liver cell damage, can help determine changes in liver failure.
Liver function tests can assist in the diagnosis of a variety of liver and gallbladder diseases, however, the liver has a strong regenerative capacity and reserve function, even if it is invaded by cancer cells, there may still be more than 30% of liver cells, in a normal state of operation, therefore, liver function test results may not be significantly abnormal. Therefore, liver function tests can not fully reflect the liver lesions, if screening for cirrhosis or liver cancer, but also do other tests, such as ultrasound tests, liver fibrosis tests, alpha-fetoprotein tests, etc. Finally, we remind everyone that if there is fatigue, low-grade fever, nasty greasy, jaundice, spider nevus and other manifestations, you need to be vigilant about abnormal liver function, you should seek medical attention in time and carry out relevant examinations.
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