Association between urinary oxytocin secretion and natriuresis after transsphenoidal pituitary surgery.

Oxytocin (OXT) secretion has been shown to be abnormally elevated in patients who develop syndrome of inappropriate secretion of antidiuretic hormone (SIADH)-related hyponatremia after transsphenoidal pituitary surgery (TPS). While OXT was previously reported to increase natriuresis in the kidney, a potential role for this hormone in postoperative sodium balance and dysnatremias has not been studied. The objective of this study was to analyze the correlation between patients' urinary output of OXT and natremia and natriuresis after TPS. The authors measured and correlated the urinary output of OXT with natriuresis and natremia in 20 consecutive patients who underwent TPS. The ratio of urinary secretion of OXT between days 1 and 4 showed a strong, significant correlation with patient natriuresis at day 7 after pituitary surgery. Concomitantly, patient natremia showed a moderate, inverted correlation with OXT secretion in the urine. Together, these results show for the first time that urinary OXT secretion correlates with patient natriuresis and natremia after pituitary surgery. This observation suggests a notable role for this hormone in sodium balance.