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Kidney Week

Abstract: SA-OR41

Anemia, Iron Deficiency, and FGF-23 in CKiD Study

Session Information

Category: Pediatric Nephrology

  • 1700 Pediatric Nephrology

Authors

  • Thomas, Elizabeth, University of California Los Angeles, Los Angeles, California, United States
  • Hanudel, Mark R., University of California Los Angeles, Los Angeles, California, United States
  • Laster, Marciana, University of California Los Angeles, Los Angeles, California, United States
  • Salusky, Isidro B., University of California Los Angeles, Los Angeles, California, United States
  • Furth, Susan L., The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States
  • Warady, Bradley A., Children's Mercy Hospitals and Clinics, Kansas City, Missouri, United States
Background

Fibroblast growth factor 23 (FGF23) is an important bone-derived hormone implicated in the pathogenesis of chronic kidney disease-mineral bone disorder (CKD-MBD), CKD progression, and CKD-associated cardiovascular morbidity. It has recently been demonstrated that anemia-related factors, specifically iron deficiency and erythropoietin, can also increase FGF23 production. The objectives were to determine whether anemia and/or iron deficiency are associated with increased FGF23 levels.

Methods

In the largest national pediatric CKD cohort (the Chronic Kidney Disease in Children (CKiD) Study), anemia, iron and FGF23 profiles were characterized in a cross-sectional analysis. Participants included children aged 1 month to 16 years old with mild to moderate CKD.

Results

In a cross-sectional analysis of 686 pediatric CKD patients (median (IQR) age 11 (8, 15) years, 62% male, 14% Hispanic), the median eGFR was 55 (41, 71) ml/min/1.73m2, and the median age-related hemoglobin standard deviation score (SDS) was -1.1 (-2.3, 0.2). Anemic subjects had higher C-terminal FGF23 levels than non-anemic subjects (153 vs 103 RU/mL, p<0.0001). In bivariate analyses, log-transformed C-terminal FGF23 was inversely associated with hemoglobin SDS, serum iron, eGFR, and serum calcium and was positively associated with age-related phosphate SDS. In a multivariable linear regression model, log-transformed C-terminal FGF23 was inversely associated with hemoglobin SDS (see Table 1). Log-transformed intact FGF23 was not significantly associated with hemoglobin SDS or serum iron.

Conclusion

Decreased hemoglobin concentrations are independently associated with increased C-terminal FGF23 levels in pediatric CKD. Future analyses will assess relationships among longitudinal changes in hemoglobin SDS, iron parameters, and FGF23.

Table 1: Univariable and multivariable linear regression modeling of determinants of circulating log-transformed C-terminal FGF23
Parameter
Univariable analysis Multivariable analysis  
 Std P-valueStd P-valueVIF
Age (years)0.040.27-0.180.0011.33
Sex (male) (yes versus no)0.08
0.04-0.020.661.05
eGFR (ml/min/1.73m2)-0.38<0.0001-0.33<0.00011.13
Calcium (mg/dL)-0.070.046-0.070.221.33
Phosphate SDS0.23<0.00010.150.0051.14
Serum Iron (g/dL) -0.120.02-0.050.321.20
Hemoglobin SDS -0.27<0.0001-0.130.021.43

Funding

  • NIDDK Support