LIVER FUNCTION.pptx

phd biochemistry

1. LIVER FUNCTION TEST Dr. Jagroop Singh Research associate Govt medical college amritsar

2. FUNCTIONS OF LIVER Liver is a versatile organ which is involved in metabolism. Independently involved in many other biochemical functions. Liver is the largest organ in the human body. It weighs 1.2 to 1.5kg in adult.

3. 1. Metabolic functions Liver is the key organ and the principal site where the metabolism of carbohydrates, lipid and proteins take place. Liver is the organ where NH3 is converted to urea. It is the principal organ where cholesterol is synthesized, and catabolized to form bile acids and bile salts.

4. Liver besides other organs can bring about catabolism and anabolism of nucleic acids. Liver is also involved in metabolism of vitamins and minerals to certain extent. 2. Secretory functions: Liver is responsible for the formation and secretion of bile in the intestine. Bile pigments bilirubin formed from heme catabolism is conjugated in liver cells and secreted in the bile.

5. 3. Excretory function : Certain exogenous dyes like BSP ( Bromsulphthalein ) and rose bengal dye are exclusively excreted through liver cells.

6. 4. Synthesis of certain blood coagulation factors: Liver cells responsible for conversion of preprothrombin (inactive) to active prothrombin in the presence of vit . K. It also produces other clotting factors v, vii, and IX, X. Fibrinogen involved in blood coagulation is also synthesized in liver.

7. 5.Synthesis of other protein: Albumin is synthesized in liver and also to some extent alpha and beta globulins.

8. 6. Detoxification function and protective function: Kupffer cells of liver remove foreign bodies from blood by phagocytosis . Liver cells can detoxicate drugs, hormones and convert them into less toxic substances for excretion.

9. 7.Storage function: Liver stores glucose in the form of glycogen. It also stores Vitamin B12 , Vitamin A etc.

10. 8. Miscellaneous functions: Liver is involved in blood formation in embryo and in some abnormal states, it also forms blood in adults.

11. CLASSIFICATION OF LFT’s: 1. TESTS BASED ON LIVER s PART IN CARBOHYDRATE METABOLISM: Glucose tolerance test ; The ability to utilize carbohydrates can be determined by glucose tolerance test. A loading dose of glucose is estimated. The blood glucose levels are estimated at regular intervals after the glucose load.

12. In conditions of insulin deficiency, blood glucose levels get elevated due to impaired utilization of glucose. ( A) Decreased glucose tolerance; Decreased carbohydrate tolerance (non utilization of carbohydrate load) is observed in conditions causing hyperglycemia, for example; diabetes mellitus, hyperthyroidism.

13. (B) Increased glucose tolerance; Hypothyroidism Adrenal cortical hypofunction Galactose tolerance test; The normal liver is able to convert galactose into glucose, but this function is impaired in intrahepatic diseases and the amount of blood galactose and galactose in urine is excessive. Advantage of this test; It is used to primarily to detect liver cell injury.

14. It can be performed in presence of jaundice. Methods; two types; oral galactose tolerance test; The test is performed in the morning after night fast. A fasting blood sample is collected which serves as control. 40g of galactose dissolved in a cup full of water is given orally. Further blood sample are collected at half hour intervals for two hrs.

15. Interpretations: Normally or in obstructive jaundice; 3g or less of galactose are excreted in the urine within 3 to 5hrs and the blood galctose returns to normal within one hrs. In intrahepatic jaundice; the excretion amounts to 4 to 5g or more during the first five hrs.

16. (b) IV galactose tolerance test ; The test is performed in the morning after a night fast. A fasting blood sample is collected which serves as control. An IV injection of galactose , equivalent to 0.5g/kg body weight is given as a sterile 50% solution. Blood sample are collected half hrs, 1hrs, one and half hrs, 2 hrs and two nd half hrs aftr IV injection and blood galactose level estimated.

17. Interpretations: A normal response; should have a curve beginning on the average at about 200mg galactose /100dl, falling steeply during the on hours and reaching a figure b/w 0 to 10mg% by end of 2hrs. In most cases of obstructive jaundice; similar results are obtained, unless there is parenchymal damage.

18. Fructose tolerance test;(method) 50g of fructose given to the fasting patient as for GTT. Fasting blood sugar is estimated and blood sugar is estimated on sample taken half hrs Fructose tolerance test;(method) 50g of Fructose tolerance test;(method) 50g dose given to the fasting patient as for GTT. is intervals for two and half hrs after taking the oral fructose. The usual methods for estimation of blood sugar measures both the glucose and fructose present. Interpretation; N ormal response; shows little or no rise in the blood sugar level. The highest blood sugar value reached during the test should not exceed the fasting level by more than 30mg%.

19. Epinephrine tolerance test ;(storage function) Principle; the response to epinephrine as evidence elevation of blood sugar is a manifestation of glycogenolysis and is directly influenced by glycogen stores of liver. Interpretations ; Normally in the course of an hr, rise in blood sugar over the fasting level exceeds by 40mg% or more. In parenchymal hepatic diseases; the rise is less.

20. 2.TESTS BASED ON CHANGES IN PLASMA PROTEIN; (a). Determination of total plasma proteins and albumin and globulin and A:G Ratio. This yields most useful information in chronic liver diseases. Liver is the site of albumin synthesis and also possibly of some of alpha and beta globulins.

21. Interpretations ; In infections hepatitis; quantitative estimations of albumin and globulin may give normal results in the early stages. Qualitative changes may be present, in early stage rise in globulins and in later stages gamma globulins show rise. In advanced parenchymal liver diseases and in cirrhosis liver; the albumin is grossly decreased and the globulins are often increased, so that A:G ratio is reversed, such a pattern is characteristically seen in cirrhosis liver.

22. (b). Estimation of plasma fibrinogen ; formed in the liver and likely to be affected if considerable liver damage is present. Normal value is 200-400mg%. (c). Flocculation tests ; the tests have become outdated and not routinely carried out. Principle; flocculation tests depend on an alteration in the type of proteins present in plasma. The alteration may be either quantitative or qualitative and most frequently involves one or more of the globulin fractions.

23. Two types test ; 1. thymol turbidity and flocculation test. 2. zinc sulphate turbidity test. 3. TESTS BASED ON ABNORMALITIES OF LIPIDS; Cholestersol – Cholesteryl ester ratio; the liver plays an active and important role in the metabolism of cholesterol including its synthesis, esterification , oxidation and excretion.

24. 4. TESTS BASED ON THE DETOXIFICATION FUNCTION OF THE LIVER; Hippuric acid test; It is test for assessing the detoxification function of liver. 6g of sodium benzoate is dissolved in 250ml water and orally given to the subject, after a light breakfast and emptying the bladder. Urine collections are made for next 4 hrs and the amount of hippuric acid is estimated.

25. Heathly persons excrete 60% of sodium benzoate in urine. Decrease in hippuric acid excretion indicates liver damage. Disadvantage ; rarely suggest a specific diagnosis.

26. TESTS BASED ON EXCRETORY FUNCTION OF LIVER; 1. BSP retention test ( bromosulphthalein test) Injected BSP is excreted by liver through bile and function of liver is tested by its ability to excrete the dye. In healthy human beings, less 15% of the dye should be retained after 25min and 5% after 45min. In parenchymatous liver diseases, excretion proceeds more slowly.

27. In advanced liver cirrhosis, removal is very slow and 40-50% of the dye is retained after 45min. 2 . Rose bengal dye test ; Rose bengal dye is another dye is used to assess excretory function. 10ml of a 1% solution of the dye is injected IV slowly. Normally 50% or more of the dye disappears within 8min. In parenchymatous liver diseases high count in the neck persists and there is hardly rise in the count over abdomen, as the dye is retained.

28. FORMATION OF PROTHROMBIN BY LIVER; Prolonged prothrombin time indicates liver damage. Normal level of prothrombin in control give prothrombin time of appox . 14sec.

29. VALUE OF SERUM ENZYMES IN LIVER DISEASES; They can be divided into 2 groups. 1. most commonly and routinely done in the laboratory. 2. not routinely done in the laboratory. Most commonly and routinely employed in laboratories are two; Serum transaminases ( amino transferases ). Serum alkaline phosphatase .

30. 1. serum transaminases ; SGOT (IFCC METHOD) Principle ; SGOT catalyzes the transfer of amino group b/w L- aspartate and alpha ketoglutarate to form oxaloacetate and glutamate. The oxaloacetate formed reacts with NADH in the presence of malate dehydogenase to form NAD. The rate of oxidation of NADH to NAD is measured as a decrease in absorbance which is proportional to the SGOT activity in the sample.

31. Normal value; 5- 40IU/L SGOT is an enzyme found mainly in heart muscle, liver cells, skeletal muscle and kidney. Injury to these tissue results in the release of the enzyme in blood. Elevated levels are found in myocardial infarction, cardiac operations, hepatitis, cirrhosis, renal disease.

32. Decreased levels may be found in pregnancy, beri - beri and diabetic ketoacidosis . 2 . SGPT ; (); SGPT is found in tissues but is mainly found in the liver. Increased levels are found in hepatitis, cirrhosis, obstructive jaundice and other hepatic diseases. Slight elevation of the enzymes is also seen in myocardial infarction.

33. Principle ; SGPT convert L- alanine and alpha ketoglutarate to pyruvate and glutamate. The pyruvate formed reacts with 2, 4, dinitrophenyl hydrazine to produce a hydrazone derivative, which in an alkaline medium produce a brown coloured complex whose intensity is measured. Normal range; 5-35IU/L

34. ( B). Serum alkaline phosphatase ; ( pNPP kinetic method). It is found in high concentrations in the liver, biliary tract epithelium and in the bones. Normal levels are age dependent and increase during bone development. Increased levels are mainly liver and bone disease. Moderate increases are seen in hodgkins disease and congestive heart failure.

35. Principle ; ALP at an akaline pH hydrolyses p- nitrophenylphosphate to form p- nitrophenol and phosphate. The rate of formation of p- nitrophenol is measured as an increase in absorbance which is proportional to the ALP activity in the sample. Normal values; serum (adults); 80-290U/L (children); 245-770U/L

36. 2. Other enzymes (not done routinely); Serum 5’- nucleotidase (N.V 2- 17IU/L) LDH (N.V 70-240IU/L) Serum iso - citrate dehydrogenase (ICD). Serum cholinesterases (true and pseudo cholinesterases ) Serum ornithine carbamoyl transferase (OCT) Serum leucine amino peptidase (LAP) Serum aldolase

37. Serum amylase (N.V serum – upto 90U/L Serum sorbitol dehydrogenase Serum gamma glutamyl transferase (GGT) GGT (N.V serum) male; 10-50U/L female; 7-35U/L GGT is an enzyme found mainly in serum from hepatic origin. Elevated levels are found in hepatobiliary and pancreatic diseases, chronic alcoholism, liver damage, diabetics.

38. TESTS BASED BASED ON ABNORMALITIES OF BILE PIGMENT METABOLISM; VD bergh reaction and serum bilirubin Determination of serum bilirubin Bile pigments in urine/ faeces Urinary and faecal urobilinogen TESTS BASED ON DRUG METABOLISM; MEGX ( monoethyl glycine xylidine ) TEST; Procedure; 1. An I.V bolus injection of a small lidocaine test dose, 1mg/kg, is given.

39. Blood sample is taken before the injection. Another blood sample is taken 15 or 30min. after the injection. MEGX is determined in the serum by use of an automated fluorescence polarization immunoassay within about 20min. in both the sample. Interpretations ; The highest MEGX test results are observed in liver donors with unimpaired organ function and in normal healthy subjects.

40. 2. Antipyrine breath test ; antipyrine like lidocaine is also metabolized by cytochrome p450 system. When given orally it is absorbed from intestine completely, not bound to plasma proteins and metabolized by liver only. Interpretations ; Normal subjects excrete 5-8% of the administered dose in 2 hrs. patients with hepatitis and cirrhosis excretes only 2-3%.