ACTH stimulation test will rule ______ Addison's disease.

• A. In
• B. Out
• C. Between
• D. Across

Answer: (A)

The key idea is that the ACTH stimulation test checks whether the adrenal glands can respond to ACTH. In Addison's disease, the adrenal cortex is damaged and cannot produce cortisol even when stimulated, so cortisol levels fail to rise after giving synthetic ACTH. This blunted response effectively confirms the diagnosis, meaning Addison's disease is ruled in. If cortisol rises normally after stimulation, Addison's is unlikely, helping to rule it out. In practice, this test helps distinguish primary adrenal failure from other causes of adrenal insufficiency by showing whether the adrenals themselves can respond to ACTH.