Liver function tests are used to determine the state and function of a patient's liver. Several biochemical tests are used in this evaluation, some of which involve the detection of liver enzymes. Liver enzymes that are commonly detected include alpha-1 antitrypsin, alkaline phosphatase, alanine transaminase, aspartate aminotransferase and gamma-glutamyl transpeptidase. These enzymes all have different roles within the liver, and their detection is used to evaluate the state of specific liver functions. Elevation above the normal range for some of these enzymes can be a sign of liver complications.
Symptoms of Abnormal Liver Function
The most common symptoms of liver abnormality include abdominal pain and yellowing of the skin and eyes, known as jaundice. Other external symptoms include excessive sweating, bad body odor, dark circles under the eyes, brownish spots and blemishes on the skin, and flushed facial appearance or excessive facial blood vessels. Internal symptoms, which are clinically important and often missed by the patient, include bone loss, an enlarged spleen and fluid in the abdominal cavity.
Causes of Abnormal Liver Function
Many diseases and disorders cause the liver to function abnormally. Some are hereditary, such as hemochromatosis, Wilson's disease and Gilbert's syndrome. Other diseases can be virally contracted, including hepatitis A, B, C, D and E, as well as yellow fever. Obesity can also lead to problems with the liver, as can drug and alcohol abuse. These complications can often lead to cirrhosis, in which healthy liver is replaced by fibrous scar tissue.
Elevated Liver Enzymes
The liver function test detects the presence of liver enzymes in the blood. Under normal conditions, the level of these enzymes in the blood is low, but when liver cells are damaged, these enzymes are released into the blood and their levels increase as a result. Therefore, elevated liver enzymes in the blood are used as markers of liver disease. As some of the enzymes detected in the liver function test are also present in other tissues, it is important that results for different enzymes are combined to determine the patient's condition.
Alkaline Phosphatase
Alkaline phosphatase is an enzyme that removes phosphate groups from a variety of different molecules. It is present throughout the body, but is particularly abundant in the bones, kidneys, bile ducts and liver. As such, it is used as a marker of diseases that damage these tissues. Although some tests, such as the alkaline phosphatase isoenzyme test, can discriminate between the different types of alkaline phosphatase in the body, other tests cannot. Therefore, it is important that results from several tests are collated when diagnosing liver disease.
Prevention and Treatment for Liver Abnormalities
Many diseases that cause liver damage can be avoided. Hepatitis B and C are both transmitted via blood and bodily fluids, meaning that their spread can be prevented by promoting safe sex and providing clean needles for intravenous drug users. There is also a vaccine available against hepatitis B. It is also important to remember to drink alcohol in moderation and abstain from dangerous drug use. Obese patients who have liver complications are encouraged to lose weight and eat a healthy diet.
Drugs used to treat different liver diseases include anti-virals and immunomodulators. If treatment for liver disease does not work or patients refuse to abstain from dangerous substances, the last resort is a liver transplant.
