Endocrine Abstracts

Introduction: Adrenocorticotropin (ACTH)-independent macronodular adrenal hyperplasia (AIMAH) is a rare cause of Cushing’s syndrome, commonly involving the aberrant expression of several membrane-bound adrenal receptors. Recent studies have investigated whether the latter is also implicated in the renin-independent aldosterone secretion of hyperaldosteronism cases.

Case report: A 35-year-old man presented to our department for evaluation of new-onset arterial hypertension without other symptoms or clinical signs. An adrenal computerised tomography revealed bilateral macronodular adrenal hyperplasia. Adrenal hormonal investigation showed cortisol and marginal aldosterone oversecretion (urinary free cortisol (UFC) 192 μg/24 h, basal ACTH <5 pg/ml, serum cortisol following low dose dexamethasone suppression test 216 nmol/l and post-saline infusion serum aldosterone 136 pmol/l). Following an extensive diagnostic protocol for the detection of aberrant hormone receptors, a positive response of cortisol and aldosterone was evident in the isoproterenol infusion and the insulin tolerance test pointing to β-adrenergic stimulation. A positive response of cortisol was also shown in the vasopressin administration mediated via V1-receptor activation. The nor-iodo-cholesterol adrenal scintigraphy demonstrated increased uptake on the right adrenal gland. Following a 3-month trial of propranolol therapy, a right adrenal-sparing adenomectomy was performed. The post-operative follow-up revealed persistent cortisol oversecretion and resolution of prior aldosterone autonomy.

Conclusions: We report a clinical case of AIMAH with combined cortisol and aldosterone oversecretion in response to β-adrenergic and V1-receptor mediated vasopressin stimuli. The in vivo identification of aberrant adrenal receptors would confirm our clinical findings and aid to clarify the mechanisms underlying this rare form of adrenocortical disorder.