Improvement of hypercortisolism by β-blocker therapy in subclinical Cushing's syndrome associated with ACTH-independent macronodular adrenocortical hyperplasia

A 61-year-old man with hypertension and diabetes was referred for the evaluation of multiple bilateral adrenal tumors. While Cushingoid features were not apparent, an elevated cortisol level in response to a low-dose dexamethasone suppression test (187.7 nmol/l), an elevated urinary cortisol level (170.9 nmol/day), and a weak response to a cosyntropin-releasing hormone (CRH) provocation test were observed. Furthermore, the serum cortisol level increased in response to a posture test or isoproterenol infusion. Accordingly, the patient was diagnosed as having ACTH-independent macronodular adrenal hyperplasia (AIMAH) with subclinical Cushing's syndrome associated with the aberrant expression of beta-adrenergic receptors. After 2 months of propranolol therapy, the serum cortisol responses to a posture test and isoproterenol infusion, the cortisol level in response to a low-dose dexamethasone suppression test (102.1 nmol/l), and the urinary cortisol level (165.9 nmol/day) all normalized. While the suppression of cortisol secretion was sustained for 24 months, glucose metabolism and adrenal size were unaffected. To our knowledge, this is the first report of AIMAH accompanied by subclinical Cushing's syndrome associated with the aberrant expression of beta-adrenergic receptors. Furthermore, propranolol inhibited cortisol hypersecretion in the present case. Additional cases or controlled studies are needed to determine the potential effect of propranolol on metabolic disorders and adrenal size in patients with AIMAH.