Glucose Tolerance Test PDF

Glucose Tolerance Test Preparing by : Dr. Sondos Taleb Sh. Faris Introduction o The ability to utilize carbohydrates can be determined by Glucose tolerance test. Initially fasting blood glucose is estimated o A loading dose of glucose is given. o The blood glucose levels are estimated at...

Glucose Tolerance Test Preparing by : Dr. Sondos Taleb Sh. Faris Introduction o The ability to utilize carbohydrates can be determined by Glucose tolerance test. Initially fasting blood glucose is estimated o A loading dose of glucose is given. o The blood glucose levels are estimated at regular intervals after the glucose load. o In conditions of insulin deficiency, blood glucose levels get elevated due to impaired utilization of glucose Decreased Glucose Increased Glucose tolerance Tolerance Decreased carbohydrate tolerance Increased carbohydrate tolerance is (nonutilizat of carbohydrate load) is observed in conditions causing observed in a conditions that cause hyperglycemia, hypoglycemia- for example:  Hypopituitarism Diabetes  Hyperinsulinism mellitus Hyperactivity of  Hypothyroidism anterior pituitary  Adrenal cortical hypofunction and  Decreased gastro intestinal Hyperthyroidism adrenal cortex absorption like sprue celiac and Stress disease. 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). o The glucose tolerance test can be used to screen for type 2 diabetes.  Indication of Glucose tolerance test 01 02 03 In asymptomatic In persons with Persons with family persons with symptoms of diabetes history but no sustained or but no glycosuria or symptoms or positive transient glycosuria. hyperglycemia. blood findings. 04 05 06 In persons with or In patients with In women with H/o without symptoms of neuropathies or having delivered large diabetes mellitus retinopathies of babies. showing one abnormal unknown origin. blood findings.  Contraindications of glucose tolerance test 01 02 03 In proven cases of GTT is required only The test should not diabetes mellitus in doubtful cases, it be carried out in the test is not is not recommended acutely ill patients. required. for follow up of patient.  Factors affecting GTT A Acute infections- Cortisol is secreted, the curve is elevated and prolonged. B Hypothyroidism- A flat curve is obtained in hypothyroidism. Thyroid hormone increases the absorption of glucose from C the gut. Starvation- There is rise of counter regulatory hormones, D which show increased glucose tolerance. Some more Precaution Before GTT o For proper evaluation of the test, the subjects should be normally active and free from acute illness. o Medications that may impair glucose tolerance include diuretics, contraceptive drugs, glucocorticoids, niacin, and phenytoin should be avoided on that day. Type of glucose tolerance test Preparation of Patient o Patient should on carbohydrate rich unrestricted diet for 3 days. o Patient should be ambulatory with normal physical activity. o Medications should be discontinued on the day of testing. o Exercise, smoking and tea or coffee are not allowed during test period. o OGTT carried out in the morning after patient has fasted overnight for 8-14 hours. Cont... o A fasting venous blood sample is collected in the morning. o 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). Cont... o In the classical procedures, the blood and urine samples are collected at half hourly interval of the next three hours. o A curve is plotted with the blood glucose levels on the vertical axis against the time of collection on the horizontal axis. o The curve so obtained is called glucose tolerance curve. Normal Glucose tolerance Curve Diabetic Curve  Laboratory profile of a normal person after glucose load Fasting 30 60 90 120 150 180 (Zero Minutes Minutes Minutes Minutes Minutes Minutes sample) Blood Glucose 90 100 150 120 110 80 70 (mg/dl) Urinary nil nil nil nil nil nil nil Glucose 1. Normal Glucose Tolerance Curve i) Fasting blood glucose (Zero hour sample) is 90 mg/dl, which is well within the normal range(Normal 60-100 mg/dl). ii) 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. 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. Cont… Atypical normal response shows following features. o Initial fasting glucose within normal limits. o The highest peak value is reached within 1 hour. o The highest value does not exceed the renal threshold (160- 180 mg/dl). o The fasting level is again reached by 2-2.5 hours. o No glucose or ketone bodies are detected in any specimen of urine. 2. Diabetic Curve o Fasting blood glucose is higher than normal o The highest value is attained at 1 hour to 1 hour 30 minutes. o The highest value exceeds the renal threshold o Glucose is found in almost all the urine samples. o The blood glucose level does not return to the fasting level even within 2hour 30 minutes. Diabetic Curve  Laboratory profile of a diabetic patient after glucose load Fasting 30 60 90 120 150 180 (Zero Minutes Minutes Minutes Minutes Minutes Minutes sample) Blood Glucose 200 225 350 300 275 250 225 (mg/dl) Urinary + + + + + + + Glucose  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. Diabetic V/S Normal Curve  Criteria for Criteria for Diagnosing Normal persons Diagnosing Impaired Glucose Diabetes Tolerance (IGT) >110 mg/dl 6.1mmol/L) (160mg/dl) Not Prescribed Not Prescribed administration) (>9.0mmol/L) 2hr (after glucose >140mg/dl) 7.8mmol/L) (