The liver is the largest internal organ and is called the powerhouse of your body. That's because each liver cell has about 1500 mitochondria cells that convert the food we eat into energy for our body by metabolizing or breaking down carbohydrates, proteins and fats. Any damage to the liver or an infection can cause you to feel very sick that may require medical intervention.
In a liver function test, a certified Lab Technician (LT) would analyze the following proteins, enzymes and other substances in your blood. While certain enzymes or substances indicate good health, particular others suggest an infection or disease. Let's check what they mean:
Bilirubin: Bilirubin is a yellow pigment that is made when RBCs break down. In a healthy person, bilirubin is chemically altered by the liver and safely removed by urine and stool. But when the liver cells are damaged, excess bilirubin is not processed and, as a result, builds up in our blood resulting in yellow colouration of eyes and skin.
The total protein test: This test measures the amount of albumin and globulin in the blood plasma. These two proteins are made in the liver, except immunoglobulin (a form of globulin protein) is made in the immune cells.
Albumin is synthesized in the liver and helps maintain oncotic plasma pressure, i.e. they prevent fluid from leaking out of the blood vessels into the nearby tissues. If excess fluid were to flow out from blood vessels into the nearby tissues, it could result in edema (swelling caused by fluid trapped in your body's tissue). The other role of albumins is also to carry different substances such as bilirubin, ions, fatty acids etc., throughout your body.
Globulins are a group of proteins that are spherical or global in shape. They are larger than albumins and are synthesized in the liver or the immune cells. The different types of globulins are clotting proteins that help in blood clotting, immunoglobulins that help fight infections, and lipoproteins that carry fats and cholesterol throughout your body.
If the total protein is lower than normal, it could lead to pedal edema (swelling of ankles and feet), Ascites (swelling of the abdomen) or puffiness of the face.
If the total proteins are higher than normal, it could mean cancer, hepatitis, HIV, inflammation or dehydration.
In healthy persons, the albumin/globulin ratio is between 1.1 and 2.5. Anything less than 1 indicates chronic liver disease, cancer or kidney disease.
Alanine aminotransferase (ALT): As mentioned earlier, the liver is called the body's powerhouse, i.e., they convert the food we eat (carbohydrates, proteins and fats) into energy. Alanine aminotransferase is an enzyme that helps break down proteins in the liver so that our bodies can utilize them as energy. However, when the liver is damaged, it is unable to utilize ALT. As a result, more ALT would be released into your bloodstream, and its level would rise. ALT is more specific to the liver. Thus higher levels of ALT in the blood usually indicate damage to liver cells.
Aspartate aminotransferase (AST): Aspartate aminotransferase, like Alanine aminotransferase, also helps in protein metabolism. But unlike the ALT, AST is also specific to muscle, liver, heart, and kidneys. Thus higher levels of AST in the bloodstream can also indicate injury to heart, muscle, and kidney cells.
Alkaline phosphatase (ALP): Alkaline phosphatase is made in the liver (mostly in the bile duct), bones, intestines, and pregnant women's placenta. They help in the metabolism of protein, fat and bone development. Abnormal levels of ALP in the blood indicate biliary tract obstruction (gallstones), hepatitis, cirrhosis, osteoporosis or pregnancy.
Gamma-glutamyltransferase (GGT): Gamma-glutamyltransferase is found in the bile duct, spleen, heart, pancreas and brain but not in the bone and placenta. Therefore it becomes an important marker to differentiate between liver and bone diseases.
Lactate dehydrogenase: It is an enzyme that helps in the conversion of glucose to energy. It is found in all essential organs such as the heart, RBCs, lungs, kidneys, pancreas, liver, skeletal muscles and placenta. Any damage to these cells may result in excess lactate dehydrogenase spilling out into the bloodstream. Doctors would typically analyze different isomers of lactate dehydrogenase to narrow down on your disease. For example, LDH isomer 4 is specific to the kidney, LDH isomers 2, 3 is specific to the lungs.