Distinguish Cushing disease from Cushing syndrome.

• A. Cushing disease is ACTH-secreting pituitary adenoma causing hypercortisolism.
• B. Cushing disease is exogenous steroid excess; Cushing syndrome is ACTH-secreting pituitary adenoma.
• C. Cushing disease is an adrenal cortisol-secreting tumor.
• D. Cushing disease is cortisol deficiency.

Answer: (C)

The key idea is that Cushing disease refers to a specific cause of cortisol excess, while Cushing syndrome describes the broader set of conditions with too much cortisol from any cause. Cushing disease is due to a pituitary ACTH-secreting adenoma that drives the adrenal glands to overproduce cortisol, causing hypercortisolism. Cushing syndrome, on the other hand, includes cortisol excess from pituitary ACTH (Cushing disease), ectopic ACTH production, adrenal cortisol-producing tumors, or exogenous glucocorticoid use. So an adrenal cortisol-secreting tumor would cause Cushing syndrome but not Cushing disease, and exogenous steroid excess also causes Cushing syndrome. Cortisol deficiency is not involved in these conditions.