Mineralocorticoid responsive hyponatremia of the elderly

Background: Mineralocorticoid responsive hyponatremia of the elderly (MRHE) is an emerging concept of hyponatremia in aged people. Diagnosis of MRHE requires exclusion of syndrome of inappropriate antidiuresis and adrenal dysfunction. Thus we aimed to evaluate the characteristics of all patients with suspected MRHE available for a review. Methods: We conducted a systematic review using MEDLINE and Google scholar. We included published case reports of adult patients diagnosed as MRHE, written by English and Japanese language. Serum and urine electrolytes as well as the levels of antidiuretic hormone (ADH), cortisol, plasma renin activity (PRA), and aldosterone were analyzed. Results: A total of 27 MRHE patients were identified in 9 reports. In these patients, average age was 79 years, median serum sodium was 117 mEq/L. The median levels of ADH, cortisol, PRA, and aldosterone were 0.9 pg/mL, 18.7 &mgr;g/dL, 0.37 ng/mL/h, and 39.6 pg/mL, respectively. Water restriction test was conducted in 7 patients. Random sample cortisol measurements did not exceed satisfactory levels to rule out adrenal dysfunction in four cases. No cases underwent low-dose adrenocorticotropic hormone stimulation test. Only 27 patients from 9 case reports in Japanese were eligible for inclusion in our study. Conclusion: All published cases of MRHE as a cause of hyponatremia are described for the first time. In these cases, latent adrenal sufficiency might have been hidden and should have been excluded.