Early inappropriate secretion of antidiuretic hormone after trans-sphenoidal pituitary adenomectomy. The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a rare but life-threatening complication of trans-sphenoidal pituitary adenomectomy. It has previously only been described as a late phenomenon. We report an early presentation within the first week. The pathophysiology, clinical features and treatment are discussed. 