Liver Function Tests | Online Biotech Notes
Online Biotech Notes
Liver Function Tests
Liver performs several diversified functions. It is the central organ of body's metabolism.
Major functions of liver
1. Metabolic functions
Liver actively participates in carbohydrate, lipid, protein, mineral and vitamin metabolisms.
2. Excretory functions
Bile pigments, bile salts and cholesterol are excreted in the bile into intestine.
3. Protective functions and detoxification
Kupffer cells of liver perform phagocytosis to eliminate foreign compounds. Ammonia is detoxified to urea.
Liver is responsible for the metabolism of xenobiotics (detoxification).
Liver is responsible for the metabolism of xenobiotics (detoxification).
4. Hematological functions
Liver participates in the formation of blood (particularly in the embryo), synthesis of plasma proteins (including blood clotting factors) and destruction of erythrocytes.
5. Storage functions
Glycogen, vitamins A, D and B12 and trace element iron are stored in liver.
Hepatocellular damage may occur due to viruses (hepatitis A virus, hepatitis B virus), toxins (carbon tetrachloride, aflatoxin), alcohol, hepatocellular carcinoma, autoimmune hepatitis etc.
Tests to assess liver function
The liver function tests (LFT) are the biochemical investigations to assess the capacity of the liver to carry out any of the functions it performs. LFT will help to detect the abnormalities and the extent of liver damage.
Two important facts should be borne in mind while carrying out LFT.
1. Liver is a large-size factory of safety. Therefore, it can perform many of its functions almost normally, despite the damage.
2. Selection of the right test is important in LFT. This is due to the fact that since liver participates in several functions, the function that is measured in LFT may not be the one that is adversely affected.
bromosulphthalein.
2. Tests based on serum enzymes derived from liver - Determination of transaminases, alkaline phosphatase, 5’-nucleotidase, γ- glutamyltranspeptidase.
3. Tests based on metabolic capacity— Galactose tolerance, antipyrine clearance.
4. Tests based on synthetic functions— Prothrombin time, serum albumin.
5. Tests based on detoxification—Hippuric acid synthesis.
Causes of liver damage
Hepatocellular damage may occur due to viruses (hepatitis A virus, hepatitis B virus), toxins (carbon tetrachloride, aflatoxin), alcohol, hepatocellular carcinoma, autoimmune hepatitis etc.
Tests to assess liver function
The liver function tests (LFT) are the biochemical investigations to assess the capacity of the liver to carry out any of the functions it performs. LFT will help to detect the abnormalities and the extent of liver damage.
Two important facts should be borne in mind while carrying out LFT.
1. Liver is a large-size factory of safety. Therefore, it can perform many of its functions almost normally, despite the damage.
2. Selection of the right test is important in LFT. This is due to the fact that since liver participates in several functions, the function that is measured in LFT may not be the one that is adversely affected.
The major liver function tests may be classified as follows
1. Tests based on excretory function— Measurement of bile pigments, bile salts,bromosulphthalein.
2. Tests based on serum enzymes derived from liver - Determination of transaminases, alkaline phosphatase, 5’-nucleotidase, γ- glutamyltranspeptidase.
3. Tests based on metabolic capacity— Galactose tolerance, antipyrine clearance.
4. Tests based on synthetic functions— Prothrombin time, serum albumin.
5. Tests based on detoxification—Hippuric acid synthesis.
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