Apelin levels in patients with polyuria-polydipsia syndrome upon copeptin stimulation tests.

Objective: Differentiating between arginine vasopressin deficiency (AVP-D) and primary polydipsia (PP) requires a copeptin stimulation test. We aimed to characterize changes in apelin, an endogenous hormone antagonizing AVP, upon copeptin stimulation tests.

Design: Post hoc secondary analysis of a multi-centric cross-over diagnostic study (NCT03572166).