Topic- Glucose tolerance test (gtt) biochemistry

Gtt

1. Topic- Glucose tolerance test Presented by: Mr. Rajeev Kr. Keshari ( Asst. Prof.) Gopal Narayan University , Sasaram ( Bihar)

2. Introduction of Glucose Tolerance test A Glucose tolerance test (GTT) is a procedure that determine whether a patient can use and store glucose normally. The test is usually use to test for diabetes mellitus , insulin resistance, impaired pancreatic beta cell function, and some times reactive hypoglycemia or rarer disorders of carbohydrate metabolism. This test version of the test, an oral glucose tolerance test (OGTT) is standard dose of glucose is ingested by mouth , and blood levels are checked two hours later.

3. What is glucose tolerance test The oral glucose tolerance test (OGTT) is a 2 hour test. It checks blood glucose levels. It examines the blood sugar before and 2 hours after you have had a sweet drink. It how exactly your body processes sugar. Other usual tests such as random blood sugar or Hb1Ac test, glucose tolerance tests are usually prescribed fro those who are pregnant.

4. Definition The glucose tolerance test (GTT) is performed to determine how your body responds to glucose . You drink a glucose solution, and your blood is taken at intervals to see how quickly the glucose is removed from the blood.

5. Indication of glucose tolerance test Patients with a family history of diabetes. Patients with delayed healing of wounds ( specially on the lower legs or feet) Patients who have transient glycosuria or hyperglycemia during pregnancy, myocardial infection, surgery and stress. Patients with or without symptoms of diabetes mellitus showing one abnormal blood finding in patients with neuropathies or retinopathies of unknown origin. In women with H/o having delivered large babies.

6. Contra indication of OGTT test In proven case of diabetes mellitus the test is not required. GTT is required only in doubtful case, it is not recommended for follow up of patient. Patient with serious concurrent infections or end of ocrine disorders, because glucose in tolerance will be observed even though these patients may not be diabets . The test should not be carried out in acutely ill patients.

7. Precaution of patient during GTT test Or patient preparation The patient instructed to have good carbohydrate diet for 3 days prior to the test. Diet containing about 30-50gram of carbohydrate should be taken on the evening prior to the test. The patient should avoid drugs likely to influence the blood glucose levels for at least 2 days prior to the test. Patient should abstain from smoking during the test. Strenuous exercise on the previous day is to be avoided. The exercise is also to be avoided on the same day prior to the test.

8. Types of glucose tolerance test Standard oral glucose tolerance test I/V Glucose tolerance test Mini Glucose tolerance test

9. Procedure of std. oral glucose tolerance test At about 8 am the fasting blood and urine samples are collected. These are called zero samples. A loading dose of 75g. Anhydrous glucose dissolved in 250-300 ml of lemon juice or water is given to the patient In children 1.75g of glucose /kg body weight is given. Instruction the patients to ingest the entire glucose load.

10. Procedure Tell the patient that he or she cannot eat anything until the test is completed. However encourage the patient to drink water. No other liquids should be taken during the testing period. Inform the patient that tobacco , and smoking are not allowed . Collect a venous blood & urine sample at 30 min. interval for 2 hours or up to 3 hours. Glucose is estimated in all the blood samples. Urine is analyzed for the presence of glucose.

11. Normal glucose tolerance curve Time Fasting ½ hr 1 hr after taking glucose 1 ½ 2 hr 2 ½ hr Blood sugar ( mg/dl) 75 130 140 100 65 70 Urine sugar - ve - ve - ve - ve - ve - ve Fasting blood glucose zero hour sample is 75mg/dl Which is well within the normal range 60- 100mg/dl There is rise of blood glucose after glucose load and the peak value is observed at I hours. This is due to absorption of glucose from the intestine

12. Normal glucose tolerance curve Insulin is released upon increase of blood glucose level. There is fall in blood glucose with time due to glucose utilization promoted by insulin The normal blood glucose level is achieved after 250 min.

13. The range of blood sugar levels in GTT seen in normal persons and diabetic patients (WHO recommendation test dose 75 g glucose) Normal Criteria for diagnosing diabetes mellitus Normal in pregnancy Fasting <100mg/dl >140 mg/dl <115mg/dl 1 hr after glucose <160 mg/dl No definite level <190 mg/dl 2 hrs after glucode <140 mg/dl >200mg/dl <165 mg/dl

14. Diabetic patient after glucose load Moderate diabetic curve Fasting 30 min. 60 min 90 min. 120 min 150 min Blood glucose 140 200 280 260 220 170 Urinary glucose Nil ++ ++ ++ ++ nill Fasting 30 min. 60 min 90 min. 120 min 150 min Blood glucose 230 300 345 365 350 330 Urinary glucose ++ +++ +++ +++ +++ +++ Serve Diabetic curve

15. Oral glucose tolerance test.

16. Diabetic curve of GTT Fasting blood glucose is higher than normal The highest value is attained at 1 hour to 1:30 hour min. The highest value exceeds the renal thershold . Glucose is found in almost all the urine sample The blood glucose level does not return to the fasting level within 2 hr 30 min.

17. Abnormal glucose tolerance result Renal glycosuria :- Blood glucose level are within the normal limits but urine glucose is positive. Glucose tolerance curve normal. Thus glucose is found in some of the samples depending upon the renal threshold. There is lowering or renal threshold due to renal tubular defect in glucose absorption. GTT is also useful in the diagnosis of this inherited renal tubular defect.

18. Cause of renal glycosuria Early diabetes mellitus Pregnancy Renal disease deficiency of carrier protein Havey metal poisoning Renal glycosuria can also be observe in children of diabetic parents.

19. Lag curve Fasting blood glucose normal ½ to 1 hr blood glucose crosses renal thershold . 1 ½ to 2 hr blood glucose normal. ½ to 1 hr urine glucose positive. Example- increased glucose absorption from intestine and after partial gastrctomy . Cause of lag curve : Hypothyroidism Pregnancy After gastro enterostomy Early diabetes mellitus.

20. Flat curve Fasting blood glucose <75mg/dl All sample show low blood glucose Urine glucose is negative. Flat curve are seen in patients with hypo activity of other endocrine. E.g. in hypopituitarism and addison disease, malaabsrption .

21. Cause of lag curve Hypothyroidism Pregnancy After gastro enterostomy Early diabetes mellitus. Flat curve

22. Gestational diabetic curve Fasting blood glucose >150mg/dl ½ to 1hr blood glucose >190 mg/dl 1 ½ to2 hr blood glucose >165 mg/dl ½ to 1 hr urine glucose postive .

23. Oral glucose tolerance test.

24. IV Glucose tolerance test This test undertaken for patients with malabsorption. Under these conditions oral glucose load is not well absorbed and the results of oral glucose tolerance test become inconclusive. The values for the IV GT test differ slightly from those of the oral GT test because IV glucose is absorbed faster

25. Procedure I/V glucose tolerance test is carried out by giving 25 g of glucose dissolved in 100 ml intravenous injection within 5 minutes. Completion of infusion is taken as 0 time. Blood sample are taken at 10 min. interval for the next hour. The peak value is reached within a few minutes and the value touches to near normal in 45- 60 min.

26. Interpretation In normal blood glucose level returns Normal within 60 min. In Diabetes mellitus , decline is slow The initial values are attained in 120 min.

27. Mini GTT As per current WHO recommendations, in the mini or modern glucose tolerance test only two sample are collected. Fasting ( zero hour) and 2 hour post glucose load Urine sample are also collected during the same tinme The diagnosis is made from the variation . Observed in these result.

28. Clinical Significant of GTT Increase Glucose tolerance Increase carbohydrate tolerance is observed in all condition that cause hypoglycemia. Hypopituitarism Hyperinsulinism Hypothyroidism Adrenal Cortical Hypo function

29. Clinical Significant of GTT Decrease Glucose tolerance Diabetes mellitus Acute stress response Cushing syndrome Chromic renal failure Glucagonoma Acute pancreatitis Diuretic therapy Corticosteroid Myxedema After gastrectomy