OGT Medications and Factors Affecting OGTT Results 1 — Questions and Answers
Question 1: Which drug class is well-known for causing hyperglycemia that can produce a false-positive OGTT?
- ACE inhibitors
- Corticosteroids (Correct answer)
- Beta-blockers
- Loop diuretics
Correct answer: Corticosteroids
Corticosteroids (e.g., prednisone) raise blood glucose by stimulating hepatic gluconeogenesis and inducing insulin resistance, potentially producing false-positive OGTT results.
Question 2: Which antihypertensive class can mask hypoglycemic symptoms and potentially confound OGTT interpretation?
- ACE inhibitors
- Calcium channel blockers
- Beta-blockers (Correct answer)
- ARBs
Correct answer: Beta-blockers
Beta-blockers suppress adrenergic symptoms of hypoglycemia (tremor, tachycardia) and can blunt the counter-regulatory glucose response, complicating OGTT interpretation.
Question 3: Thiazide diuretics affect OGTT results by:
- Lowering blood glucose through increased renal excretion
- Raising blood glucose by impairing insulin secretion and increasing insulin resistance (Correct answer)
- Having no effect on glucose metabolism
- Stimulating GLP-1 release
Correct answer: Raising blood glucose by impairing insulin secretion and increasing insulin resistance
Thiazide diuretics cause hypokalemia, which impairs beta-cell insulin secretion, and can increase insulin resistance, leading to falsely elevated OGTT values.
Question 4: Niacin (nicotinic acid) at pharmacological doses used for dyslipidemia can affect OGTT by:
- Improving insulin sensitivity
- Raising plasma glucose through insulin resistance (Correct answer)
- Lowering fasting glucose
- Having no metabolic effect
Correct answer: Raising plasma glucose through insulin resistance
High-dose niacin impairs insulin secretion and increases hepatic glucose output, potentially causing elevated OGTT values and new-onset diabetes.
Question 5: Which immunosuppressant used in organ transplant patients commonly causes post-transplant diabetes and abnormal OGTT?
- Cyclosporine (Correct answer)
- Methotrexate
- Hydroxychloroquine
- Azathioprine
Correct answer: Cyclosporine
Cyclosporine and tacrolimus (calcineurin inhibitors) are directly toxic to pancreatic beta cells and cause post-transplant diabetes mellitus (PTDM).
Question 6: Antipsychotic medications such as olanzapine affect OGTT results primarily through:
- Direct pancreatic beta-cell stimulation
- Weight gain and insulin resistance (Correct answer)
- Increased renal glucose clearance
- GLP-1 receptor blockade
Correct answer: Weight gain and insulin resistance
Second-generation (atypical) antipsychotics like olanzapine promote significant weight gain and insulin resistance, increasing the risk of abnormal OGTT and type 2 diabetes.
OGT Medications and Factors Affecting OGTT Results 1
Which drug class is well-known for causing hyperglycemia that can produce a false-positive OGTT?