Which statement best differentiates Cushing's disease from Cushing's syndrome?

Which statement best differentiates Cushing's disease from Cushing's syndrome?

• A. Cushing's disease is adrenal in origin
• B. Cushing's syndrome is pituitary-driven
• C. Ectopic ACTH production is the sole cause
• D. Cushing's disease is due to a pituitary ACTH-secreting adenoma; Cushing's syndrome is caused by other etiologies

Answer: (D)

Differentiating Cushing's disease from Cushing's syndrome hinges on the source of the excess cortisol. Cushing's disease is specifically a pituitary ACTH-secreting adenoma that drives the adrenal glands to overproduce cortisol. Cushing's syndrome is the broader condition of hypercortisolism from any cause, including ACTH-dependent sources (like ectopic ACTH production) and ACTH-independent sources (such as adrenal tumors or even exogenous glucocorticoid use). Therefore, the best statement is that Cushing's disease is due to a pituitary ACTH-secreting adenoma, while Cushing's syndrome can arise from other etiologies. This distinction matters for management, since treatment targets differ depending on the underlying source.

Differentiating Cushing's disease from Cushing's syndrome hinges on the source of the excess cortisol. Cushing's disease is specifically a pituitary ACTH-secreting adenoma that drives the adrenal glands to overproduce cortisol. Cushing's syndrome is the broader condition of hypercortisolism from any cause, including ACTH-dependent sources (like ectopic ACTH production) and ACTH-independent sources (such as adrenal tumors or even exogenous glucocorticoid use). Therefore, the best statement is that Cushing's disease is due to a pituitary ACTH-secreting adenoma, while Cushing's syndrome can arise from other etiologies. This distinction matters for management, since treatment targets differ depending on the underlying source.