Copeptin in the differential diagnosis of the polydipsia-polyuria syndrome: revisiting the direct and indirect water deprivation tests

Department of Internal Medicine I–Endocrine Unit (W.F., D.L., M.F., B.A.), and Comprehensive Heart Failure Center (W.F., M.F., S.S., B.A.), University Hospital Wurzburg, D-97080 Wurzburg, Germany; Division of Diabetes, Endocrinology, and Metabolism (W.F.), Department of Medicine, Imperial College London, London W12 ONN, United Kingdom; Clinical Endocrinology (M.Q., K.Z.), Charite Campus Mitte, Charite University Medicine Berlin, 10117 Berlin, Germany; B.R.A.H.M.S. GmbH (U.H., J.P.), Research Department, 16761 Berlin, Germany; Division of Endocrinology, Diabetes, and Nutrition (A.F.H.P.), Charite Campus Benjamin Franklin, Charite University Medicine Berlin, 10117 Berlin, Germany; and Department of Internal Medicine I–Cardiology (S.S.), University Hospital Wurzburg, D-97080 Wurzburg, Germany