Glucose Tolerance Test Part-I.pptx

Glucose tolerance tests are also used to diagnose diabetes. The OGTT is used to screen for or diagnose diabetes in people with a fasting blood glucose level that is high, but is not high enough (above 125 mg/dL or 7 mmol/L) to meet the diagnosis for diabetes.

1. Glucose Tolerance Test Mr. Abhijit Bhoyar Assistant Professor Department of Child Health Nursing Part-I Glucose Tolerance Test Mr. Abhijit Bhoyar Assistant Professor Department of Child Health Nursing Part-I

2. Specific Learning Objectives At the end of the lecture, the students will be able to Define Glucose Tolerance Test.(GTT). Explain the decreased and increase glucose tolerance. Define Glucose Tolerance Test.(GTT). Enumerate indications of Glucose Tolerance Test.(GTT ).

3. Cont.….. Enlist Contraindications of Glucose Tolerance Test.(GTT). Identify the factors affecting Glucose Tolerance Test (GTT). Describe the preparation for Glucose Tolerance Test.(GTT). Explain the procedure of Glucose Tolerance Test.(GTT ). Explain the Glucose Tolerance Test curve and its types.

4. Introduction The ability to utilize carbohydrates can be determined by Glucose tolerance test. Initially fasting blood glucose is estimated A loading dose of glucose is given. The blood glucose levels are estimated at regular intervals after the glucose load. In conditions of insulin deficiency , blood glucose levels get elevated due to impaired utilization of glucose.

5. Decreased Glucose tolerance Decreased carbohydrate tolerance ( non-utilization of carbohydrate load) is observed in conditions causing hyperglycemia , for example: Diabetes mellitus, Hyperactivity of anterior pituitary and adrenal cortex, Hyperthyroidism and Stress.

6. Increased Glucose Tolerance Increased carbohydrate toleranc e is observed in all conditions that cause hypoglycemia-

7. Glucose tolerance test Glucose tolerance means the ability of the body to utilize glucose in blood circulation. The glucose tolerance test, also known as the oral glucose tolerance test, measures body's response to sugar (glucose). The glucose tolerance test can be used to screen for type 2 diabetes.

8. Indication of Glucose tolerance test

9. Contraindications of glucose tolerance test In proven cases of diabetes mellitus the test is not required. GTT is required only in doubtful cases, it is not recommended for follow up of patient. The test should not be carried out in acutely ill patients.

10. Factors affecting GTT Acute infections- Cortisol is secreted, the curve is elevated and prolonged. Hypothyroidism - A flat curve is obtained in hypothyroidism . Thyroid hormone increases the absorption of glucose from the gut. Starvation- There is rise of counter regulatory hormones, which show increased glucose tolerance .

11. Some more Precaution Before GTT For proper evaluation of the test, the subjects should be normally active and free from acute illness. Medications that may impair glucose tolerance include diuretics, contraceptive drugs, glucocorticoids, niacin, and phenytoin should be avoided on that day.

12. Types of glucose tolerance test

13. Preparation of Patient Patient should on carbohydrate rich unrestricted diet for 3 days. Patient should be ambulatory with normal physical activity. Medications should be discontinued on the day of testing . Exercise, smoking and tea or coffee are not allowed during test period. OGTT carried out in the morning after patient has fasted overnight for 8-14 hours.

14. Cont.…. A fasting venous blood sample is collected in the morning. Patients ingest 75 g of anhydrous glucose in 250-300 ml of water over 5 minutes. ( for children, the dose is 1.75 g of glucose per kg ).

15. Cont… In the classical procedures , the blood and urine samples are collected at half hourly interval of the next three hours. A curve is plotted with the blood glucose levels on the vertical axis against the time of collection on the horizontal axis. The curve so obtained is called glucose tolerance curve.

16. Procedure of Standard Oral glucose tolerance test At about 8 a.m. the fasting blood and urine samples are collected. These are called zero samples . A loading dose of 75 g. anhydrous glucose dissolved in 250-300 ml of water is given to the patient.

17. Cont.…. In children 1.75 g of glucose /kg body weight is given. In the classical procedures , the blood and urine samples are collected at half hourly interval of the next two and a half hour or three hours. Glucose is estimated in all the blood samples. Urine is analyzed for the presence of glucose.

18. Glucose tolerance curve A curve is plotted with the blood glucose levels on the vertical axis against the time of collection on the horizontal axis. The curve so obtained is called glucose tolerance curve.

19. 1. Normal Glucose Tolerance Curve Fasting blood glucose (Zero hour sample)- is 90 mg /dl, which is well within the normal range(Normal 60-100 mg/dl). There is rise of blood glucose after glucose load and the peak value is observed at I hour . This is due to absorption of glucose from the intestine.

20. Cont.…. iii) Insulin is released upon increase of blood glucose level. There is fall in blood glucose with time due to glucose utilization promoted by insulin . iv) The normal blood glucose level is achieved after 150 minutes.

21. Cont…. A typical normal response shows following features. Initial fasting glucose within normal limits. The highest peak value is reached within 1 hour. The highest value does not exceed the renal threshold (160-180 mg/dl). The fasting level is again reached by 2-2.5 hours. No glucose or ketone bodies are detected in any specimen of urine .

22. 2. Diabetic Curve Fasting blood glucose is higher than normal The highest value is attained at 1 hour to 1 hour 30 minutes . The highest value exceeds the renal threshold Glucose is found in almost all the urine samples . The blood glucose level does not return to the fasting level even within 2hour 30 minutes.

23. Response of diabetic patients Fasting blood glucose is definitely raised above 110 mg/dl . The highest value is reached after 1-1.5 hours. The highest value exceeds the renal threshold. The blood glucose level does not return to fasting level within 2.5 hours. This is the most characteristic feature of DM. Urine sample always contains glucose except in some chronic diabetes or nephritis who may have raised renal threshold.

24. Cont…. According to severity, GTC may be: Mildely dibetic curve Moderately severe diabetic curve Severe diabetic curve

25. 3. Lag Curve Fasting blood glucose is normal . Sharp rise within 30 minutes to one hour The blood glucose levels exceed the renal threshold . The decline is rapid and the normal levels are attained back. Some of the urine samples contain glucose , where the blood glucose is above the renal threshold.

26. Cause of Lag Curve Hyperthyroidism Pregnancy After gastro- enterostomy Early diabetes mellitus

27. 4. Curve for Renal Glucosuria Glucose appears in the urine at levels of blood glucose much below renal threshold. Patients who show no glucosuria when fasting may have glucosuria when blood glucose is raised. It may be seen in : Renal disease and pregnancy Early diabetes

28. Expected Questions Short Explain the decreased and increase glucose tolerance. Enumerate indications and contraindications of Glucose Tolerance Test (GTT). Describe the procedure of Glucose Tolerance Test.(GTT ). Very Short Define Glucose Tolerance Test.(GTT).

29. References Jacob Anthikad, Biochemistry for nurses 3 rd ed. Pankaja Naik, Essentials of Biochemistry, 1 st ed. Satyanarayan, Essentials of Biochemistry, 2 nd ed. A. C. Deb, Biochemistry, 4 th ed.

30. THANK YOU