Reset Osmostat in an Infant with Failure to Thrive

We are reporting an infant who was presented to our institution exhibiting a failure to thrive and hyponatremia. An extensive renal evaluation revealed resistive hyponatremia with normal renal glomerular and tubular function. Patient remained hyponatremic even after fluid restriction, salt loading and Fludrocortisone (Florinef) administration. Water deprivation and water loading tests were suggestive of “hyponatremia of reset osmostat”. The infant had no congenital midline defect.