Which test is used as a confirmatory test for adrenal insufficiency?

• A. Insulin tolerance test
• B. ACTH stimulation test
• C. Metyrapone stimulation test
• D. Dexamethasone suppression test

Answer: (A)

The insulin-induced hypoglycemia test directly challenges the entire hypothalamic-pituitary-adrenal axis. By causing a controlled drop in blood glucose, it normally triggers CRH release, stimulates ACTH secretion, and drives cortisol production from the adrenal glands. If cortisol fails to rise adequately, adrenal insufficiency is confirmed, because this test requires a functioning axis at every level (hypothalamus, pituitary, and adrenal glands). It’s considered the most sensitive confirmatory test for AI, applicable to both primary and secondary forms, since it assesses the system’s integrated response rather than just one part of the axis.

The other tests serve different purposes. An ACTH stimulation test looks at how the adrenal glands respond to exogenous ACTH and is widely used as an initial screen for primary AI, but it may miss some cases of secondary AI where the pituitary drive is the problem. The metyrapone test evaluates pituitary ACTH reserve and the production of downstream steroids, mainly used in more specialized endocrine evaluations. The dexamethasone suppression test is used to evaluate hypercortisolism (Cushing’s syndrome) rather than adrenal insufficiency.