A glucose tolerance test is used to help diagnose:

A glucose tolerance test is used to help diagnose:

• A. Cushing's disease
• B. Addison's disease
• C. Hypothyroidism
• D. Diabetes mellitus

Answer: (D)

A glucose tolerance test assesses how well the body handles a glucose load by measuring blood glucose at intervals after drinking a standardized amount of sugar. In diabetes mellitus, insulin action or secretion is impaired, so glucose stays elevated longer and the post-load glucose value is higher than normal. That makes this test specifically useful for diagnosing diabetes (and gestational diabetes) rather than other endocrine conditions. Cushing's disease and Addison's disease are diagnosed through cortisol and ACTH testing, while hypothyroidism is diagnosed with thyroid function tests; they aren’t primarily evaluated with glucose tolerance testing.

A glucose tolerance test assesses how well the body handles a glucose load by measuring blood glucose at intervals after drinking a standardized amount of sugar. In diabetes mellitus, insulin action or secretion is impaired, so glucose stays elevated longer and the post-load glucose value is higher than normal. That makes this test specifically useful for diagnosing diabetes (and gestational diabetes) rather than other endocrine conditions. Cushing's disease and Addison's disease are diagnosed through cortisol and ACTH testing, while hypothyroidism is diagnosed with thyroid function tests; they aren’t primarily evaluated with glucose tolerance testing.