Liver Function Checks And Bilirubin Biology Essay

The body is made up of various organs and one of the most important homeostatic organs is the liver organ. However, despite its very dynamic role, is mainly underemphasised and even though most of its functions aren't as regulatory as the mind, the liver organ is involved in important processes. Included in these are biochemical, excretory and synthetic functions, therefore, to identify deviations in its function, several testing must be completed. These test are known as ''Liver function tests''. They provide signs on the liver organ function and help to measure the level or amount of liver damage. Hence, they are being used in the medical diagnosis of liver organ disease. And since early diagnosis and healing intervention plays a sizable role in the treatment of liver diseases, liver function tests are important.

Liver function tests

The liver is the major visceral organ in the torso. It weighs about 1. 3kg (3lb) within an adult (patho publication ref). It offers about 500 individual functions. To ensure that the liver continues to carry out these functions, there are several assessments which are completed on the liver when investigating a patient with liver disease. These tests are carried out on the bllod, each of them checking the volumes or degrees of various constituents in the blood vessels. Liver function testing include lab tests depict cholestasis (alkaline phosphatase, gamma glutamyl transpeptidase), checks reflecting the artificial function of the liver organ assessments (albumin and prothrombin time), assessments portraying excretion (bilirubin, alkaline phosphatase and gamma glutamyl transpeptidase) and tests monitoring the quantity of cell damage or liver personal injury (Aspartate aminotransferase and alanine aminotransferase).


This is a yellow mixture or pigment produced by the break down of haemoglobin. This originates from the break down of worn out, old or broken red blood skin cells. The senescent bloodstream cells are adopted and destroyed macrophages (Kupffer skin cells) of the phagocytic system (which can be found primarily in the spleen and in the liver. During the break down of haemoglobin into heme and globin, the globin is further degraded to form new protein and the heme part forms bilverdin. In the Kupffer cells, the bilverdin is changed into bilirubin by the use of enzymes. The bilirubin is then released into the plasma where it binds to albumin and becomes an unconjugated bilirubin.

The unconjugated or free bilirubin enters the hepatocytes and after blending with glucuronic acid, it becomes a conjugated bilirubin. This conjugated bilirubin is normal water soluble and therefore, soluble in bile, therefore if the outflow of bile is interrupted, conjugated bilirubin will have an impact on the colour of the urine, it becomes darker. Conjugated bilirubin gets into into the small intestines through the bile ducts and there, it is deconjugated into urobilinogen by bacterias. The urobilinogin produced could either be reabsorbed into circulation by the hepatic portal vein into the liver organ to be re-excreted into the bile or excreted in faeces. This process is recognized as the enterohepatic flow. The urobilinogen excreted in faeces or urine is oxidized to urobilin which is responsible for the colour of faeces.

There are two tests which are carried out for bilirubin. These are direct-reacting (which is completed for conjugated bilirubin) and indirect-reacting (which is carried out for unconjugated bilirubin). Various conditions can result in an elevation in the amount of bilirubin in the blood, such as blockage of the bile ducts, unnecessary creation of bilirubin, reduced conjugation, reduced secretion and reduced uptake by the liver organ. Increased levels of indirect bilirubin are usually triggered by liver organ cell disorder. A good example is within hepatitis where the broken biliary excretion leads to the presence of surplus faecal urobilinogen in the urine. This gives the urine a darker colour and can be utilized as a sign of early on cell personal injury. And an increase of immediate bilirubin characteristically results from an obstruction which could either be located within or outside the liver organ (e. g. a blockage in the bile ducts or gallstones). When the bile duct is obstructed, the concentration of urinary urobilinogen reduces because the stoppage in the excretion of bile in to the gut will not lead to synthesis of the faecal urobilinogen.


Albumin is a major protein which is synthesised by the liver organ cells and secreted into the blood. The capacity of the artificial function of the liver can be measured with the use of albumin. The serum albumin test, therefore, is completed in order to measure the amount of protein in the serum. Albumin has a comparatively long 1 / 2 life of 21 years old days, therefore, liver harm must persist (be long run) before reduced levels of serum can be observed. Inability to maintain the serum levels between your reference value of 35- 50 g/L brings about a low reading of albumin, known as hypoalbuminaemia, which signifies impending liver inability. Apart from liver failing, there are other conditions which can cause low serum albumin. For example urinary loss, hypercatabolism and also severe malnutrition.

Alkaline Phosphatase

Alkaline phosphatase can be an isoenzyme which exists in the liver canalicular plasma membrane of hepatocytes, in the placenta, intestine and in the bone for bone building. The normal amount of alkaline phosphates is less 100 IU/L. Upsurge in alkaline phosphatase is mostly due to increase in enzyme production in areas near to an obstruction and also due to the molecular weight of the biliary isoenzyme. This is recognized with the used of serum electrophoresis. Increase in alkaline phosphatase can be brought on by disorders such as cholestasis within the liver (intrahepatic) or beyond your live (extrahepatic), space occupying lesions (such as abscesses, cysts and tumours) and hepatitis. During pregnancy, the isoenzyme positioned in the placenta is released and the isoenzyme in the bone is also released in children and children during growth. They are known as physiological increases in serum alkaline phosphatase. In disorders such as rickets, the serum alkaline phosphatase level is increased. This type of increase is named a pathological increase. And even though bilirubin levels increase alongside alkaline phosphatase levels, sometimes the bilirubin value can stay normal no matter an elevated alkaline phosphatase level.

Gamma Glutamyl transpeptidase

Gamma-glutamyltraferse, gGT, is a glycoprotein which is found in many tissues including the prostate, liver, intestine, pancreas, and kidneys. It offers a normal range which is <50IU/L. Unlike alkaline phosphatase, gGT is more liver-specific. gGt is higher in men than in women and babies and neonates have high levels up until 1yr. Though it can be utilized in testing for cholestasis because its level goes up in cholestasis alongside ALP, it is more very sensitive in indicating liquor and drug (e. g. Phenytoin) absorption. The increase of both ALP and gGT can be interpreted with the knowledge that in cholestasis ALP is usually greater than gGT while in an alcoholic disease, gGT is more than ALP. Various other conditions that could result in increased gGT levels include: myocardial infarction, uncomplicated diabetes mellitus and severe pancreatitis. Paracetamol and phenobarbitone are drugs that could also lead to increased levels of g-glutamyl transpeptidase. Anorexia Nervosa and over weight could serve as non hepatic triggers for the increased amounts of the enzyme

Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST)

Alanine Aminotransferase and Aspartate aminotransferase are is one of the main element enzymes which are used to indicate hepatocellular necrosis. They are simply primarily found in the liver organ, the cystol of hepatocytes(ALT) and in the mitochondria (AST). The transfer of the alpha amino acid of aspartate and alanine to alpha keto group and ketoglutaric acid respectively is catalysed by ALT. ALT and AST have a standard selection of < 40IU/L. When the value is >20 times (1000U/L), it is known as severe and the raised ALT level can lead to severe viral hepatitis, circulatory distress and medicine or toxin induced necrosis. The degrees of AST and ALT are realistically increased (2 - 30 times) in hepatitis (e. g. alcoholic hepatitis). An increased degree of AST normally shows serious abnormality of liver, heart and/or skeletal muscles.

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