Isolated hypoaldosteronism: An overlooked cause of hyponatraemia

We report three patients with hyponatraemia due to isolated hypoaldosteronism. Addison's disease was ruled out in each of these patients by a normal short synacthen test. Two patients had severe hyponatraemia and fluid restriction helped improve the sodium level only marginally. One was treated with demeclocycline, which did not prove to be effective. Subsequently, all three patients were found to have aldosterone deficiency and treatment with fludrocortisone caused their sodium levels to return to normal.