Anyway, the simultaneous measurement of copeptin—a neuropeptide co-released with AVP in equimolar concentrations and therefore considered a circulating surrogate marker of AVP activity—and serum [Na+] in a cohort of 6962 patients revealed a statistically significant correlation between all cause 30-day mortality and hyponatremia, even independently of copeptin levels [35]. Here, AVP is linked to Hyponatremia.