Context: Vasopressin plays a central role in water homeostasis but it has also been recognized to be associated with adverse effects in several chronic diseases. Recently, copeptin has been increasingly used as a surrogate for vasopressin, as they are co-secreted, and copeptin is easier to measure. However, the relationship between plasma concentrations of copeptin (P(cop)) and vasopressin (P(vp)) has only been studied in relatively small numbers of selected people.
Objective: This study sought to evaluate the relationship between P(vp) and P(cop) in a community-based population and in people with chronic kidney disease (CKD).
Design, setting, and participants: P(vp), P(cop), and urinary osmolarity (Uosm) were compared in 500 participants of the DESIR study, and in 83 ambulatory people with CKD.
Results: Median [interquartile range] of P(cop) and P(vp) in the DESIR study were 4.13 [3.58] pmol/L and 0.92 [1.93] pmol/L, respectively. Log-transformed P(cop) and P(vp) concentrations correlated significantly and positively (r = 0.686, P < .001) and they correlated inversely with estimated U(osm) (P < .001). Copeptin explained only approximately half of the vasopressin variation. In CKD, P(cop) and P(vp) both increased with decreasing estimated glomerular filtration rate (eGFR), but P(cop) increased much faster than P(vp). The P(cop)/P(vp) ratios in the lower and upper quintile groups of eGFR were 14.3 [18.3] and 5.3 [4.5], P < .001, respectively.
Conclusions: This study in a normal population, the largest ever with measurements of both peptides, shows that copeptin and vasopressin concentrations correlated well. But their relationship is distorted in CKD, suggesting that the peptide clearances differ when the renal function is impaired.