Normoaldosteronemic aldosterone-producing adenoma: immunochemical characterization and diagnostic implications

Background: A high aldosterone-renin ratio (ARR) is commonly used to identify primary aldosteronism, but the ARR is high when renin is low, even if plasma aldosterone concentration values are normal, suggesting the existence of normoaldosteronemic' primary aldosteronism. However, most such cases did not undergo adrenalectomy; moreover, because of the lack of antibody for the human CYP11B2 (aldosterone synthase), conclusive demonstration of a normoaldosteronemic aldosterone-producing adenoma was not possible thus far.Method: In 2003, a lady presented with severe hypertension a right adrenal nodule, low renin, high ARR, but normal plasma aldosterone concentration. As adrenal vein sampling showed lateralized aldosterone secretion, she underwent left adrenalectomy, which consistently normalized blood pressure (BP) and renin during 11-year follow-up.Result and conclusion: The development of a novel monoclonal antibody for the human CYP11B2 in 2014 allowed immunochemically identification of a CYP11B2-positive adenoma in the resected adrenal. Moreover, this case unequivocally demonstrates for the first time the existence of normoaldosteronemic aldosterone-producing adenoma, which suggests that many cases of low renin-essential hypertension' might instead have a surgically curable form of primary aldosteronism.