Copeptin as a possible predictor of developing diabetes insipidus following transsphenoidal pituitary surgery

Approximately 20-30% of patients develop central diabetes insipidus (DI)
following transsphenoidal surgery. DI can lead to severe morbidity and prolong
inpatient treatment. Early diagnosis of DI is thus important. Diagnosis of DI
nowadays depends on monitoring urine production and measurement of plasma
sodium and osmolality, which is labour-intensive.
Copeptin (CT-proADH) is a stable precursor of ADH and has been suggested as a
biomarker of development of DI. We hypothesize that patients who develop DI
following transsphenoidal surgery have reduced copeptin levels compared to
patients who do not develop DI.

We aim to investigate whether copeptin can be used as an early postoperative
marker for development of DI. We will measure copeptin levels in patients just
prior to and following transsphenoidal surgery to be able to investigate
whether copeptin levels are indeed reduced in patients who develop DI. Besides
we will determine a cut-off value of copeptin for identification of DI patients
(with reduced copeptin secretion) post surgery.

Observational study, multicentre approach

This study involves 12x blood sampling (venepuncture, 12x4 ml), during
scheduled inpatient treatment and once during scheduled outpatient control, 3
weeks following surgery. Eight of 12 blood samplings will be performed during
regular blood sampling (thus require no additional venepuncture). There will be
no additional site visits, physical examinations or other tests. Participation
in this study will not influence regular treatment and no risks will be
expected from additional blood sampling.