What is the likely cause of Cushing's syndrome in Ms. Hynes' case?

What is the likely cause of Cushing's syndrome in Ms. Hynes' case?

• A. Pituitary tumor
• B. Adrenal tumor
• C. Long-term corticosteroid therapy
• D. Unknown

Answer: (B)

Adrenal Cushing's occurs when a cortisol-producing tumor in the adrenal gland drives cortisol excess on its own, independent of ACTH. The resulting cortisol excess suppresses ACTH through negative feedback, so ACTH levels are low. If Ms. Hynes' case shows high cortisol with a suppressed ACTH and imaging reveals an adrenal mass, this pattern points to an adrenal tumor as the source. A pituitary tumor would raise ACTH levels (ACTH-driven) and typically cause bilateral adrenal enlargement, while long-term corticosteroid use would cause Cushing's syndrome from external steroids and also show suppressed endogenous ACTH but without an adrenal mass as the source. These clues together make an adrenal tumor the most likely cause.

Adrenal Cushing's occurs when a cortisol-producing tumor in the adrenal gland drives cortisol excess on its own, independent of ACTH. The resulting cortisol excess suppresses ACTH through negative feedback, so ACTH levels are low. If Ms. Hynes' case shows high cortisol with a suppressed ACTH and imaging reveals an adrenal mass, this pattern points to an adrenal tumor as the source. A pituitary tumor would raise ACTH levels (ACTH-driven) and typically cause bilateral adrenal enlargement, while long-term corticosteroid use would cause Cushing's syndrome from external steroids and also show suppressed endogenous ACTH but without an adrenal mass as the source. These clues together make an adrenal tumor the most likely cause.