Associations between iron status and intact FGF23 levels have not been specifically evaluated in large CKD cohorts; however, given that FGF23 cleavage is impaired in CKD [45–47], it is hypothesized that iron deficiency in CKD would increase intact FGF23 to a greater degree than iron deficiency in the absence of CKD would. The gene discussed is FGF23; the disease is Iron deficiency anemia.