RESUMEN
A 39-year-old woman presented with a 20 day history of recurrent hypoosmolar hyponatremia. Because her volume status seemed to be normal, the most suspected causes of her hyponatremia were adrenal insufficiency and hypothyroidism. Endocrinologic examination, including a combined pituitary function test, showed TSH and ACTH deficiency without GH deficiency, and hyperprolactinemia was also present. Sella MRI showed a pituitary mass, stalk thickening and loss of the normal neurohypophysial hyperintense signal on the T1 weighted image. Pathologic exam demonstrated granulomatous lesions and Langhans' multinucleated giant cells with inflammatory cell infiltration. After high dose methylprednisolone pulse therapy (1 g/day for 3 days) with subsequent prednisolone and levothyoxine replacement, there was no more recurrence of the hyponatremia. The sella MRI on the 6th month showed decreased mass size, narrowed stalk thickening and the reappearance of the normal neurohyphophysial hyperintense signal. She is currently in a good general condition and is receiving hormone replacement therapy.