FGF23 and bone disorder: We then measured fibroblast growth factor 23 (FGF23) levels, a phosphaturic factor secreted by bone to promote Pi wasting in kidney that is associated with several bone disorders.43,44 Intact FGF23 protein levels in the AnkKI/KI model for AD CMD, and in AD CMD patients were within normal range.10,45 Our data showed that there were no significant differences in intact FGF23 and C-terminal FGF23 protein levels between Cx43+/+ and Cx43KI/KI mice (Fig. 3c).