Association of fibroblast growth factor 23, parathyroid hormone, and vitamin D with acute kidney injury

Introduction
Fibroblast growth factor 23 (FGF23) plays an important role in regulating phosphate and vitamin D homeostasis. Elevated levels of FGF23 are independently associated with mortality in patients with chronic kidney disease and End stage renal disease (ESRD). Whether FGF23 levels are elevated and associated with adverse outcomes in patients with acute kidney injury (AKI) has not been studied so far.
Objective
The aim of this study was to determine the relationship between FGF23 levels in patients with AKI and morbidity, mortality, and/or the need for renal replacement therapy.
Patients and methods
The study included two groups: group 1, which included 30 AKI patients from the general medical ward and ICUs [identified in accordance with the criteria established by Acute Kidney Injury Network (AKIN) grading of AKI]; and group 2, which included 30 healthy controls matched with the patients as regards age and sex. Plasma levels of C-terminal FGF23, 1,25-dihydroxy vitamin D [1,25(OH)D], and intact parathyroid hormone (iPTH) were measured within 24 h of AKI onset and 5 days later. The composite end point was death or need for renal replacement therapy.
Results
FGF23 levels on day 1 were significantly higher among participants with AKI than among controls (mean level: 278.20 ± 220.58 vs. 14.60 ± 9 pg/ml). There was a statistically significant negative correlation between FGF23 and vitamin D on day 1, with a -value of less than 0.023, whereas there was no statistically significant negative correlation between FGF23 and vitamin D on day 5, with a -value of 0.102. There was a statistically significant positive correlation between FGF23 on day 1 and both Acute Physiology and Chronic Health Evaluation and Sequential Organ Failure Assessment scores, with a -value of less than 0.001. FGF23 proved to be a good predictor of mortality (sensitivity: 100%, specificity: 85%) at a cutoff value of 280 pg/ml.
Conclusion
FGF23 levels are elevated in AKI patients and are associated with increased mortality. AKI is also associated with significant reduction in the level of 1,25(OH)D and with significant elevation of PTH.