Leaf DE, et al. - In critically ill patients with AKI requiring RRT (enrolled in the ARF Trial Network (ATN) study) and patients with and without AKI [enrolled in the Validating Acute Lung Injury biomarkers for Diagnosis (VALID) study], researchers investigated if elevated plasma levels of the osteocyte-derived, vitamin D–regulating hormone, fibroblast growth factor 23 (FGF23), are prospectively related to death, presuming an independent association of higher FGF23 levels at enrollment with higher 60-day mortality. Higher FGF23 levels were shown to be independently related to greater mortality in critically ill patients. No association of plasma/serum levels of parathyroid hormone, vitamin D metabolites, calcium, and phosphate with 60-day mortality was observed.