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Liver Function

The liver is a vital organ situated in the upper right part of the abdomen and one we can not do without.

Its main functions are:

  • To store and filter blood, removing the toxic components from drugs, food or body waste
  • It makes bile, a liquid which is stored in the gall bladder and released into the gut to help digest fat and protein
  • It metabolizes nutrients from food
  • It stores glycogen (fuel for the body) which is made from sugars
  • It is vital in the mechanism in releasing energy ( glucose) into the bloodstream and storing vitamins and minerals
  • It makes proteins that are essential for blood to clot

The good news is that it is the only organ in the body that can regenerate itself so even if it is damaged, given the right circumstances, it can bring itself back from a severely damaged state and become as good as new. As a last resort the liver is an organ that can be transplanted extremely successfully.

There are many, many different diseases that can affect the liver including illnesses that you may have heard of such as Alcoholic Liver Disease, the whole gamut of Hepatitis A, B and C, as well as liver cancer, Primary Biliary Cirrhosis, paracetamol overdose and many that I hope you have never had cause to know about.

Liver Function Tests (LFT's) are a series of blood tests that together can give an overview of how well your liver is functioning. On single test alone is not a good indicator initially.

Different cells have different enzymes inside them, depending on the function of the cell. Liver cells happen to have lots of AST, ALT, and GGTP inside them. When cells die or are damaged, the enzymes leak out causing the blood level of these enzymes to rise; that is why the levels of these enzymes in the blood are considered good indicators of liver cell damage.

I have used the International Units of measurements throughout, but many places still measure in different units so these are for the UK.

The numbers are not linear. An AST that is 300 is not twice as bad as 150 and an AST of 94 and 80 is essentially showing the same amount of liver damage

ALT (SGPT) ALANINE AMINOTRANSFERASE (3-40 iu/L) provides an indication of the degree of inflammation

AST (SGOT) ASPARTATE TRANSAMINASE (3- 48 iu/L( provides an indication of thedegree of inflammation

ALKALINE PHOSPHATASE (30-300 iu/L) This enzyme level is elevated in a large number of disorders that affects the drainage of bile, such as a gallstone blocking the common bile duct, or alcoholic liver disease, or drug-induced hepatitis, blocking the flow of bile in smaller bile channels within the liver.

GGT GAMMA-GLUTAMYL TRANSPEPTIDASE (11- 70 iu/L) increases can be suggestive of obstructive liver disease, and is commonly used as the indicator of alcohol usage

Bilirubin (3-17 UMOL/L) increases are suggestive of liver disease, especially in disease of the bile ducts. Bilirubin is the main bile pigment in humans which, when elevated, causes the yellow discoloration of the skin and eyes called jaundice. Bilirubin is formed primarily from the breakdown of a substance in red blood cells called "heme." It is taken up from blood processed through the liver, and then secreted into the bile by the liver. Conditions which cause increased formation of bilirubin, such as destruction of red blood cells, or decrease its removal from the blood stream, such as liver disease may result in an increase in the level of serum bilirubin

Albumin is a major protein which is produced by the liver, and chronic liver disease causes a decrease in the amount of albumin produced as damage increases. Therefore, in liver disease, and particularly more advanced liver disease, the level of the serum albumin is reduced. It is associated with the malnutrition and muscle wastage commonly found in end stage liver failure.

Clotting studies may be suggestive of liver disease. Blood clotting factors are proteins made by the liver. When the liver is significantly injured, the production of these proteins is not normal. The prothrombin time is also a useful test, since there is a good correlation between abnormalities in coagulation measured by the prothrombin time and the degree of liver dysfunction.

To gain a better understanding of these tests, these are a few pertinent questions

    1. What are you looking for in my LFTs?
    2. Which part of my LFTs is abnormal and why?
    3. What is the cause of this abnormal result and how can it be treated?
    4. Could it be caused by medication I am taking?

What about my alcohol intake – is it affecting my liver function?

In summary, this series of blood tests are used to diagnose or monitor liver disease. They may be enzyme markers of disease (e.g., ALT, AST, alkaline phosphatase, and GGT), more true indicators of overall liver function (serum bilirubin, serum albumin, and prothrombin time) or specific tests that allow the diagnosis of an underlying cause of liver disease.

Interpretation of these liver tests is a complex process that your physician will utilize in the context of your medical history, physical examination, and other tests such as X-rays or other imaging studies of the liver.