What are the four tests for liver function

The four main indicators of liver function are alanine aminotransferase, aspartate aminotransferase, total bilirubin, and direct bilirubin, which are used to evaluate whether the liver has damage, inflammation, or abnormal bile excretion function.

1. Alanine transaminase:

Alanine transaminase mainly exists in liver cells and is one of the most sensitive indicators reflecting liver cell damage. When liver cells are damaged due to factors such as viruses, alcohol, drugs, or fat infiltration, the permeability of the cell membrane increases or cells rupture, and alanine aminotransferase is released into the bloodstream, leading to an increase in detection values. Mild elevation may be related to fatigue, alcohol consumption, or fatty liver, while significant elevation is common in acute viral hepatitis or drug-induced liver injury. If elevated alanine aminotransferase is detected during examination, it is recommended to check whether there is a recent history of taking special medications or excessive alcohol consumption, and pay attention to rest to avoid exacerbating the burden on the liver.

2. Aspartate transaminase:

Aspartate transaminase is also present in liver cells, but is widely distributed in tissues such as myocardium, skeletal muscle, and kidneys. Therefore, an increase in alanine aminotransferase may not necessarily be solely due to liver problems, and it needs to be comprehensively judged based on changes in alanine aminotransferase. When the ratio of aspartate aminotransferase to alanine aminotransferase significantly increases, it may indicate the progression of alcoholic liver disease or liver fibrosis. If aspartate aminotransferase is elevated alone, it is also necessary to consider whether there is intense exercise, myocardial injury, or muscle disease. In response to this situation, doctors usually recommend further electrocardiogram or muscle enzyme spectrum examination to clarify the cause.

3. Total bilirubin:

Total bilirubin is a metabolic product produced after the aging and decomposition of red blood cells, which needs to be processed by the liver before being excreted from the body. Elevated total bilirubin can lead to jaundice in the skin and sclera. The reasons for its elevation can be divided into three categories: pre hepatic anemia such as hemolytic anemia, which leads to excessive production of bilirubin; Hepatocellular diseases such as hepatitis or cirrhosis lead to a decrease in the liver's ability to process bilirubin; Posterior liver diseases such as gallstones or bile duct tumors can cause obstruction of bile excretion. If the total bilirubin is mildly elevated and mainly indirect bilirubin, it may be related to genetic abnormalities in bilirubin metabolism; If there is a significant increase in direct bilirubin, it is necessary to be alert to the possibility of biliary obstruction.

4. Direct bilirubin:

Direct bilirubin is the portion of total bilirubin that has been liver conjugated and can be directly dissolved in water and discharged into the intestine through bile. Elevated direct bilirubin usually indicates problems with the bile excretion pathway, such as bile duct stones, cholangitis, or pancreatic tumors compressing the bile duct. In addition, severe intrahepatic cholestasis such as drug-induced liver injury or primary biliary cholangitis can also lead to a significant increase in direct bilirubin. If the proportion of direct bilirubin to total bilirubin exceeds 50% during examination, it is recommended to perform abdominal ultrasound or magnetic resonance cholangiopancreatography to evaluate whether the biliary system is unobstructed.

5. Comprehensive interpretation and precautions:

Although the four liver function tests can provide important information on liver damage and bile excretion, they cannot fully reflect the liver's synthesis function such as albumin and coagulation factors, nor can they evaluate the liver's reserve capacity. Therefore, if these four indicators are abnormal, especially if they continue to rise or are accompanied by fatigue, anorexia, deepened urine color and other symptoms, it is recommended to go to the Department of Gastroenterology or the Department of Hepatology in a timely manner, and the doctor may supplement the examination according to the situation, such as hepatitis B two-and-a-half, hepatitis C antibody, liver elasticity test or liver biopsy. Daily protection of the liver should include a balanced diet, weight control, avoidance of drug and health product abuse, restriction of alcohol consumption, and regular liver function follow-up.