Endocrine Abstracts

Introduction: Disorder of water and electrolyte balance may develop after transsphenoidal (TNS) surgery for pituitary adenomas. In particular, delayed hyponatremia (Na<135 mEq/l) due to SIADH is reported in 8–35% of patients and usually resolves with fluid-intake restriction within 6 days. The possible role of vasopressin-2 receptor antagonists in this clinical setting has not been elucidated.

Case report: We report a case of a 57-years-old Caucasian woman who underwent TNS surgery for nonfunctioning pituitary macroadenoma. Postoperative period was uncomplicated and serum sodium levels in the normal range were recorded. On postoperative day 5, sodium concentrations rapidly decreased to 127 mEq/l and symptoms related to hyponatremia (haedhache, weakness) occurred. Treatment by water restriction (<1000 ml/day) and salt rich diet was started. Thirty-six hours after the beginning of fluid restriction, the serum sodium concentration was 129 mEq/l and the patient remained symptomatic. Given the lack of efficacy, water restriction was stopped and tolvaptan (Samsca 15 mg) was administered. Four hours after vasopressin-2 receptor antagonist intake, sodium levels increased to 131 mEq/l and rose to 142 mEq/l in 24 h, with disappearance of symptoms. Tolvaptan was discontinued and clinical status and serum sodium concentration was monitored. The patient was discharged two days after with a sodium value of 140 mEq/l and in good clinical condition.

Conclusions: Although in many cases of delayed acute hyponatremia after transsphenoidal surgery fluid-intake restriction is effective, in our patient this treatment resulted insufficient to reverse hyponatremia and required a significant prolongation of hospitalization. Conversely, administration of a single dose of tolvaptan rapidly and safely resolved hyponatremia. In conclusion, treatment with tolvaptan may represent a useful alternative to fluid restriction in mild symptomatic delayed hyponatremia after TNS surgery and may possibly shorten hospitalization of these patients.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.