The diagnosis of aldosterone-producing adenoma (APA) is challenging for endocrinologists, as APA does not always present with the typical constellation of clinical and laboratory features, such as hypertension, hypokalemia, suppressed plasma renin activity (PRA), and high plasma aldosterone concentration (PAC). Very recently, several studies have indicated that APA can be discovered even in normokalemic subjects with normal PRA more frequently than previously considered. Here we report a case of APA associated with chronic renal failure, which showed normokalemia and normal PRA. The patient was referred to our clinic for evaluation of an incidentally discovered adrenal mass with abnormally high PAC. After 6 yr, it was found that the right adrenal tumor showed a marked increase in size. Endocrinological examinations indicated normal PRA and markedly high PAC. Aldosterone showed a better response to the upright posture test than that to ACTH stimulation test. The diagnosis of APA was made based on the markedly high PAC to PRA ratio and the adrenocortical scintigraphy, which showed unequivocal uptake into the tumor. Right laparoscopic adrenalectomy was performed, revealing a right adrenocortical adenoma with massive hemorrhage. Histopathological examinations revealed the presence of two independent adrenocortical adenomas, one APA with predominant clear tumor cells and few c17 (17alpha-hydroxylase) immunoreactivity and the other, cortisol producing adenoma with compact cytoplasm and abundant C17 immunoreactivity. This case indicates a difficulty of diagnosis of "normoreninemic APA" with renal failure. This case is in line with the recent concept that APA is a continuous condition in which only a minority of patients have the classical clinical picture of primary aldosteronism such as hypokalemia. It is possible that normokalemic APA constitutes the most common presentation of the disease.
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