VWF and von Willebrand disease 1: Utility of DDAVP reflects its ability to stimulate release of VWF already stored in endothelial cells, thus leading to a doubling (or more) of functionally active plasma VWF in type 1 VWD (thereby, explaining its utility here), whereas release of “dysfunctional” VWF is the consequence in type 2 VWD (thereby, explaining general lack of utility here).