title: Correlation of plasma copeptin and vasopressin concentrations in hypo-, iso-, and hyperosmolar States.
abstract: BACKGROUND
  Copeptin, the C-terminal moiety of provasopressin, is cosecreted with vasopressin. Copeptin may be a useful parameter to characterize disorders of water homeostasis and can be readily measured in plasma or serum. However, it is unknown to date how circulating copeptin and vasopressin levels correlate at different plasma osmolalites.
  
  
  OBJECTIVE
  To correlate plasma copeptin with plasma osmolality and vasopressin concentrations in healthy subjects during iso-, hypo-, and hyperosmolar states.
  
  
  METHODS
  Plasma osmolalities, copeptin, and vasopressin levels were measured in 20 volunteers at baseline, after an oral water load, and during and after iv infusion of 3% saline. Correlation coefficients were determined between plasma osmolalites and copeptin and vasopressin concentrations, as well as between vasopressin and copeptin concentrations.
  
  
  RESULTS
  Median plasma osmolalities decreased from 290 mOsm/kg (range, 284-302) at baseline to 281 (273-288) mOsm/kg after water load and rose to 301 (298-307) mOsm/kg after hypertonic saline. Median plasma copeptin concentrations decreased from 3.3 (1.1-36.4) pm at baseline to 2.0 (0.9-10.4) pm after water load and increased to 13.6 (3.7-43.3) pm after hypertonic saline. Vasopressin and copeptin concentrations correlated with plasma osmolality (Spearman's rank correlation coefficient 0.49 and 0.77, respectively). There was a close correlation of vasopressin and copeptin concentrations (Spearman's rank correlation coefficient 0.8).
  
  
  CONCLUSIONS
  Plasma vasopressin and copeptin correlate strongly over a wide range of osmolalities in healthy individuals. Therefore, the measurement of copeptin, which remains stable for several days, is a useful alternative to vasopressin measurements and will likely facilitate the differential diagnosis of disorders of water metabolism.
authors.affiliation: Clinic of Internal Medicine, Hospital Center, Vogelsang 84, CH-2501 Biel-Bienne, Switzerland.
authors.forename: Sandrina
authors.initials: S
authors.lastname: Balanescu
authors.forename: Peter
authors.initials: P
authors.lastname: Kopp
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Gaskill
authors.forename: Nils G
authors.initials: NG
authors.lastname: Morgenthaler
authors.forename: Christian
authors.initials: C
authors.lastname: Schindler
authors.forename: Jonas
authors.initials: J
authors.lastname: Rutishauser
mesh_terms: D000328:Adult; D005260:Female; D006020:Glycopeptides / Q000032:analysis / Q000097:blood*; D006304:Health Status; D006801:Humans; D007038:Hypotonic Solutions / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D009994:Osmolar Concentration; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage / Q000494:pharmacology; D014667:Vasopressins / Q000032:analysis / Q000097:blood*; D014867:Water / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000502:physiology*; D014883:Water-Electrolyte Imbalance / Q000097:blood*; D055815:Young Adult
chemical_list: D006020:Glycopeptides; D007038:Hypotonic Solutions; D012462:Saline Solution, Hypertonic; C048197:copeptins; D014867:Water; D014667:Vasopressins