[When growth hormone levels drop - Management with urea of postoperative inappropriate antidiuretic hormone secretion syndrome in a patient who underwent surgery for acromegaly].

Introduction: postoperative hyponatremia is a common complication after endoscopic transsphenoidal surgery, with an incidence of 9-35 % that rises to 41.5 % in patients with acromegaly. Case report: a 74-year-old woman diagnosed with acromegaly underwent endoscopic transsphenoidal surgery and developed severe symptomatic hyponatremia (sodium 117 mmol/l) due to SIADH on postoperative day 11, after other causes of postoperative hyponatremia were ruled out. Following initial correction with hypertonic saline, treatment with oral urea (15 g/day) was started, achieving a safe increase in serum sodium (133 mmol/l at 48 hours) that allowed hospital discharge. One week later, with normalized sodium levels (137 mmol/l), treatment was withdrawn without subsequent recurrence. Discussion: oral urea is an effective, well-tolerated and cost-effective first-line treatment for SIADH after pituitary surgery, particularly relevant in patients with acromegaly given their higher incidence of late hyponatremia. Systematic sodium monitoring during the highest-risk period could allow earlier treatment initiation and prevent progression to severe cases.