A 36 year-old woman experienced a hemorrhagic shock after C/S delivery ten months ago. She was seen in an obtundent consciousness, nausea, vomiting and weakness when she was sent to N.G hospital. The results of laboratory evaluation were consistent with the inappropriate of antidiuretic hromone secretion caused by hypopituitarism. Therapy was done with hydrocortisone, hypertonic saline and Levothyroxine which rapidly corrected hypotonic hyponatremia. The hypotonic hyponatremia caused by Sheehan's syndromne should be considered in the differential diagnosis of other causes of hyponatremia.