Burckhardt MA, Gotta V, Beglinger S, et al. - Given the value of copeptin as a surrogate marker for arginine vasopressin (AVP) release in response to hyperosmolal stimuli such as diabetic ketoacidosis (DKA), researchers sought to describe kinetics of copeptin and osmolality, and their dynamic relationship during rehydration and insulin therapy in children with type 1 diabetes (T1D) and DKA. They conducted a prospective, observational, multicenter study including 28 children with T1D admitted for DKA (20 newly diagnosed T1D). Serial serum copeptin and osmolality measurements were performed from start of rehydration at 14 time points during 72 hours. Decrease in copeptin was observed from 95 pmol/L to 9.7 pmol/L with a 50% recovery time (t1/2) of 7.1 hours. Reduction in serum osmolality was noted from 321 mOsm/kg to 294 mOsm/kg with a t1/2 of 4.3 hours. Doubling in copeptin levels was noted with each osmolality increase by 15 mOsm/kg (range, 10-21 mOsm/kg) (59%), from 9.8 pmol/L (range, 7.3-12.3 pmol/L) (48%) to 280 mOsm/kg. Newly diagnosed differed from known T1D patients in copeptin kinetics, that may be explained by changes at the osmoreceptor and renal AVP receptor level due to longstanding osmotic diuresis and DKA.