Plasma oxytocin, early predictor of transient postoperative arginine vasopressin deficiency

Arginine vasopressin deficiency (AVP-D) is a well-known complication of transsphenoidal pituitary surgery (TPS) that is difficult to predict due to the lack of specific biomarkers. While oxytocin (OXT) and copeptin were previously suggested as possible biomarkers, there is, to date, no study that compared those two markers in the prediction of post-TPS AVP-D.

To compare plasma OXT and copeptin levels among patients operated by TPS presenting with AVP-D and those remaining normonatremic. To establish OXT and copeptin cutoff values for the prediction of post-TPS AVP-D.

Both OXT and copeptin levels in the blood of 74 consecutive patients subjected to TPS were measured. OXT and copeptin values were then compared between patients developing AVP-D and patients remaining normonatremic.

Neurosurgical department of a University Hospital.

Blood levels of copeptin and OXT were measured before, one day after and 3 months after TPS.

Patients developing AVP-D showed significantly lower levels of OXT in blood, both before and immediately after TPS, and significantly lower levels of copeptin only after TPS. We identified a preoperative cutoff value for OXT of 69 pg/ml (sensitivity: 90% ; specificity: 66% ; AUC: 0.76+/-0.06 (p = 0.0089)) for the prediction of AVP-D. No such significant cutoff values were identified for preoperative copeptin. Of note, OXT, but not copeptin, levels were still significantly lower at 3 months after TPS in AVP-D patients.

These results show for the first time that OXT is superior to copeptin for the preoperative prediction of postoperative AVP-D, acting as a preoperative marker of posterior "pituitary reserve".