The ACTH stimulation test result in primary adrenal insufficiency?

The ACTH stimulation test result in primary adrenal insufficiency?

• A. Cortisol rises with ACTH stimulation
• B. Cortisol falls with ACTH stimulation
• C. Cortisol fails to rise with ACTH stimulation
• D. Cortisol rises but then falls

Answer: (C)

ACTH stimulation tests what the adrenal cortex can do when stimulated with ACTH. In primary adrenal insufficiency, the adrenal glands themselves are damaged (eg, autoimmune destruction), so they cannot produce cortisol even when ACTH is provided. As a result, cortisol levels fail to rise after stimulation. This contrasts with normal or secondary adrenal insufficiency, where the adrenal cortex can still respond to ACTH if not chronically atrophic. Clinically, a blunted or absent cortisol rise after cosyntropin supports primary adrenal failure.

ACTH stimulation tests what the adrenal cortex can do when stimulated with ACTH. In primary adrenal insufficiency, the adrenal glands themselves are damaged (eg, autoimmune destruction), so they cannot produce cortisol even when ACTH is provided. As a result, cortisol levels fail to rise after stimulation. This contrasts with normal or secondary adrenal insufficiency, where the adrenal cortex can still respond to ACTH if not chronically atrophic. Clinically, a blunted or absent cortisol rise after cosyntropin supports primary adrenal failure.