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Questions and Answers
What does a glucose tolerance test primarily assess?
What does a glucose tolerance test primarily assess?
What occurs in conditions of insulin deficiency during a glucose tolerance test?
What occurs in conditions of insulin deficiency during a glucose tolerance test?
Which of the following conditions is associated with increased glucose tolerance?
Which of the following conditions is associated with increased glucose tolerance?
When is a glucose tolerance test indicated for asymptomatic individuals?
When is a glucose tolerance test indicated for asymptomatic individuals?
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What does decreased carbohydrate tolerance indicate?
What does decreased carbohydrate tolerance indicate?
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What is one indication for performing a glucose tolerance test in patients with a family history?
What is one indication for performing a glucose tolerance test in patients with a family history?
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Which of the following is associated with decreased glucose tolerance?
Which of the following is associated with decreased glucose tolerance?
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Who might require a glucose tolerance test due to having a history of delivering large babies?
Who might require a glucose tolerance test due to having a history of delivering large babies?
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In which scenario is the glucose tolerance test not recommended?
In which scenario is the glucose tolerance test not recommended?
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What effect does hypothyroidism have on the glucose tolerance test?
What effect does hypothyroidism have on the glucose tolerance test?
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What should a patient avoid on the day of the glucose tolerance test?
What should a patient avoid on the day of the glucose tolerance test?
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What is the recommended fasting duration before a glucose tolerance test?
What is the recommended fasting duration before a glucose tolerance test?
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Which medication should be avoided prior to the glucose tolerance test?
Which medication should be avoided prior to the glucose tolerance test?
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What is the purpose of collecting blood samples at half-hour intervals during the glucose tolerance test?
What is the purpose of collecting blood samples at half-hour intervals during the glucose tolerance test?
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What is the loading dose of glucose for an adult undergoing an oral glucose tolerance test?
What is the loading dose of glucose for an adult undergoing an oral glucose tolerance test?
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How is the normal glucose tolerance curve characterized after glucose load?
How is the normal glucose tolerance curve characterized after glucose load?
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What is the fasting blood glucose level considered normal?
What is the fasting blood glucose level considered normal?
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Which statement about the peak blood glucose level after a glucose load is true?
Which statement about the peak blood glucose level after a glucose load is true?
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In an atypical normal response, what is the highest blood glucose level observed?
In an atypical normal response, what is the highest blood glucose level observed?
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What is a characteristic feature of a diabetic curve after glucose load?
What is a characteristic feature of a diabetic curve after glucose load?
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At what time is the highest blood glucose value typically reached in diabetic patients?
At what time is the highest blood glucose value typically reached in diabetic patients?
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When glucose is present in urine samples, what can be inferred about the blood glucose level?
When glucose is present in urine samples, what can be inferred about the blood glucose level?
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What happens to blood glucose levels in a normal glucose tolerance test after 150 minutes?
What happens to blood glucose levels in a normal glucose tolerance test after 150 minutes?
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What is a common finding in urine for patients with diabetes?
What is a common finding in urine for patients with diabetes?
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Study Notes
Glucose Tolerance Test
- The glucose tolerance test (GTT) measures the body's response to sugar (glucose).
- The GTT can be used to screen for type 2 diabetes.
- The GTT also can be used to diagnose other conditions such as:
- Hypoglycemia
- Hyperglycemia
Indications of Glucose Tolerance Test
- Asymptomatic individuals with sustained or transient glycosuria.
- Individuals with symptoms of diabetes but no glycosuria or hyperglycemia.
- Family history of diabetes with no symptoms or positive blood findings.
- Individuals with or without symptoms of diabetes mellitus with neuropathies or retinopathies.
- Patients with unknown origin neuropathies or retinopathies.
- Women with a history of delivering large babies or showing one abnormal blood finding.
Contraindications of Glucose Tolerance Test
- Proven cases of diabetes mellitus
- Only recommended in doubtful cases—not for follow-up of the patient.
- Should not be carried out in acutely ill patients.
Factors Affecting GTT
- Acute Infections: Cortisol is secreted, the curve is elevated and prolonged.
- Hypothyroidism: A flat curve is obtained in hypothyroidism because thyroid hormone increases the absorption of glucose from the gut.
- Starvation: There is a rise in counter-regulatory hormones, which show increased glucose tolerance.
Some Precaution Before GTT
- Subjects should be normally active and free from acute illness.
- Medications that may impair glucose tolerance (e.g., diuretics, contraceptive drugs, glucocorticoids, niacin, phenytoin) should be avoided on the day of the test.
- Patients should be on a carbohydrate-rich unrestricted diet for 3 days.
- Patients should be ambulatory with normal physical activity.
- Exercise, smoking, and tea or coffee are not allowed during the test period.
- OGTT is carried out in the morning after the patient has fasted overnight for 8-14 hours.
Preparing the Patient for GTT
- 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).
- In the classical procedures, blood and urine samples are collected at half-hourly intervals for 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 obtained is called the glucose tolerance curve.
Interpreting the Glucose Tolerance Curve
Normal Glucose Tolerance Curve
- Fasting blood glucose (Zero-hour sample) is 90 mg/dl, which is within the normal range (Normal 60-100 mg/dl).
- There is a rise in blood glucose after the glucose load, and the peak value is observed at 1 hour due to the absorption of glucose from the intestine.
- Insulin is released upon an increase in blood glucose level.
- There is a fall in blood glucose with time due to glucose utilization promoted by insulin.
- The normal blood glucose level is achieved after 150 minutes.
Diabetic Curve
- Fasting blood glucose is higher than normal.
- The highest value is attained at 1 hour to 1 hour and 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 2 hours and 30 minutes.
Response of Diabetic Patients in a Glucose Tolerance Test
- 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 the fasting level within 2.5 hours.
- Urine samples always contain glucose except for some chronic diabetes or nephritis patients, who may have a raised renal threshold.
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Description
This quiz covers the glucose tolerance test (GTT), detailing its purpose, indications, and contraindications. It is essential for screening type 2 diabetes and diagnosing related conditions. Test your knowledge about the GTT and its clinical relevance.
