Abstract
We experienced a case of isolated ACTH deficiency with severe hyponatremia and hyporeninemic hypoaldosteronism whose hyponatremia was normalized by the administration of glucocorticoid despite the continued urinary sodium loss. A 57-year-old man presenting with nausea, vomiting and fatigability was admitted to our hospital because of somnolence. Since the levels of serum sodium, cortisol and urinary 17-OHCS were low, the patient was diagnosed isolated ACTH deficiency by employing continuous ACTH loading test and pituitary gland stimulation test. After the administration of corisone acetate (50mg/day) combined with an increase in oral salt intake, the level of serum sodium was normalized. We performed the hypertonic saline infusion test before and after the treatment. The result indicated that the impairment of water diuresis due to hypersecretion of ADH was improved, but hyporeninemic hypoaldosteronism and the increase of urinary sodium loss were continued after the treatment. It is concluded, in isolated ACTH deficiency, that hyponatremia occurs by existence of both glucocorticoid and mineralocorticoid deficiency and that sodium balance can be maintained by the increase in oral salt intake after the administration of glucocorticoid even if mineralocorticoid deficiency exists
