[Hyporeninemic hypoaldosteronism. Case report and attempt at pathophysiological classification (author's transl)].

A 75 year-old male presented with hyperkalemia unexplained by a moderate renal insufficiency, low basal levels of aldosterone and renin with a subnormal response to walking and saline depletion, and normal glucocorticoid function. The hyperkalemia was corrected by fluorocortisone administration. The concept of hypoaldosteronism is reviewed, defining it as an isolated aldosterone deficiency and thus excluding the combined deficiency of cortisol and aldosterone and the suprarenal enzyme deficits that simultaneously involve mineralocorticoid and glucocorticoid synthesis. Depending on the presence or absence of alterations of the renin-angiotensin axis, this infrequent syndrome can be pathophysiologically classified as low, normal or high renin hypoaldosteronism. The characteristic features of each type are described, and emphasis is made on the need for a high index of suspicion when unexplained hyperkalemia is present in order to perform the appropriate tests to confirm or rule out hypoaldosteronism.