Which statement correctly describes adrenal Cushing's syndrome?

Which statement correctly describes adrenal Cushing's syndrome?

• A. ACTH increased, cortisol increased
• B. ACTH increased, cortisol decreased
• C. ACTH decreased, cortisol increased
• D. ACTH decreased, cortisol decreased

Answer: (C)

Adrenal Cushing's syndrome occurs when the adrenal gland autonomously overproduces cortisol, independent of ACTH. That excess cortisol feeds back on the pituitary and suppresses ACTH release, so ACTH levels fall while cortisol remains elevated. This pattern—low ACTH with high cortisol—is the hallmark of adrenal (ACTH-independent) Cushing's. If ACTH were high, it would point to an ACTH-dependent form of Cushing's. If cortisol were not elevated, or ACTH were low with low cortisol, that would fit other conditions, not adrenal Cushing's.

Adrenal Cushing's syndrome occurs when the adrenal gland autonomously overproduces cortisol, independent of ACTH. That excess cortisol feeds back on the pituitary and suppresses ACTH release, so ACTH levels fall while cortisol remains elevated. This pattern—low ACTH with high cortisol—is the hallmark of adrenal (ACTH-independent) Cushing's. If ACTH were high, it would point to an ACTH-dependent form of Cushing's. If cortisol were not elevated, or ACTH were low with low cortisol, that would fit other conditions, not adrenal Cushing's.