Treatment of Hyponatremia with Tolvaptan in a Patient after Neurosurgical Treatment of a Pituitary Tumor: Case Report and Review of Literature

Hyponatremia is a frequent complication following pituitary surgery. We report a case with hyponatremia after surgery of a pituitary adenoma that was successfully treated with tolvaptan. A 68-year-old man with a pituitary tumor presented with mild hyponatremia (133 mEq/L) before surgery. The patient developed hyponatremia (125 mEq) 4 days postsurgery, and 10% sodium chloride was infused. Seven 7 days postsurgery, hyponatremia was improved (132 mEq/L), and tolvaptan 15 mg was given orally as a single dose instead of the 10% sodium chloride infusion. His serum sodium remained within normal limits. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) after pituitary surgery most probably led to the hyponatremia, and tolvaptan was effective because it is an oral vasopressin receptor antagonist.