Summary:Cushing's syndrome associated with macronodular adrenal hyperplasia (MAH) may present with high-dose dexamethasone (dex) nonsuppressible hypercortisolemia. This has been interpreted as suggesting a primary adrenal disorder, leading to recommendations for curative adrenalectomy in these cases. The present case of MAH demonstrates high urinary and serum cortisol levels, sufficiently suppressed only by ultra-high-dose (32 mg/day × 2 day) dex, with parallel reduction of plasma adrenocorticotrophin noted as well. Subsequent clinical cure by transsphenoidal hypophysectomy and identification of a pituitary adenoma confirmed the secondary nature of adrenal cortical hypersecretion. The conceptual evolution of macronodules and altered feedback dynamics of the hypothalamo-pituitary-adrenal axis in MAH are briefly discussed.