TRH and Hyponatremia: The diagnosis of sudden isolated adrenocorticotropic hormone (ACTH) deficiency could be confirmed if the clinical symptoms described above and characteristic examination findings of adrenal insufficiency (low value of ACTH and cortisol in blood, decreased free cortisol in urine, hyponatremia, increased eosinophil granulocyte, etc.)are observed, in addition to the poor response of selective ACTH and cortisol upon the combined administration of four hormones (CRH, GHRH, TRH, and gonadotropin-releasing hormone (GnRH)).