Endocrine Abstracts

Background: Routine clinical use of arginine-vasopressin (AVP) is limited by its small molecular size and pre-analytical errors. In contrast, copeptin – a peptide of 39 amino acids co-secreted with arginine-vasopressin (AVP) - is a stable protein and its measurement represents a reliable measure of AVP concentration. The aim of this study was to analyze diagnostic role of copeptin in diagnosis of diabetes insipidus (DI) in patients treated for hypothalamic-pituitary diseases.

Materials and methods: This study included patients who underwent pituitary surgery by a dedicated neurosurgical team and followed at our center. Daily assessment of polyuria-polydipsia signs/symptoms and fluid balance was performed. DI was defined as emission of high volume (>40 ml/kg/die) of hypoosmotic urine. Copeptin was measured: i) 24 hours before surgery; ii) at second post-operative (PO) day; iii) at discharge; iv) 6–8 weeks after surgery. A complete assessment of pituitary function was performed before and 6–8 weeks after surgery. Patients with DI before surgery were excluded.

Results: We selected 47 patients (F/M 27/20, mean age 55±15 years). 44 patients were affected by pituitary adenoma, 2 patients by craniopharyngioma and one patient by meningioma. 16 patients (34.0%) developed DI, which was transient in 9 (56.3%) and permanent in 7 (43.7%). DI occurred shortly after surgery (median [range]: 2 [1–3] day). Patients with Cushing’s disease presented a higher risk of post-surgical DI. An inverse correlation between tumor diameter and development of DI was found (24±8 vs 12±9 mm, P=0.002), while pituitary insufficiency and radiologic invasiveness at baseline did not show any significant difference. Median (IQR) copeptin levels was significantly lower at second PO day, at discharge and at follow-up in patients who developed DI in respect to those who did not [3.25(2.45–3.7) vs 4.5(3.6–7.4), 2.2(1.8–3.3) vs 3.8(3.2–5.6) and 3(2.5–4) vs 4.45(3.2–7) pmol/l, respectively, for all P<0.05). No difference in copeptin levels between patients with transient and permanent DI was found. Unadjusted binary logistic regression did not show a significant association between copeptin levels and DI development at baseline and at second PO day.

Conclusion: Consistently with diagnosis, postoperative copeptin levels is lower in patients who develop DI. However, in our restricted cohort of patients and at time points evaluated, copeptin did not represent an accurate marker for postoperative DI.