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Cord Blood Ferritin and Fibroblast Growth Factor-23 Levels in Neonates
Farah N Ali1, Jami Josefson1, Armando J Mendez1
1Department of Pediatrics (F.N.A., J.J., K.M.), Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611; Center for Translational Metabolism and Health (F.N.A., M.W.), Institute for Public Health and Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois; Department of Medicine (A.J.M.), Division of Endocrinology, Diabetes and Metabolism, and The Diabetes Research Institute, University of Miami Miller School of Medicine, Miami, Florida 33021; Division of Nephrology and Hypertension (M.W.), Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611.
Insights
Neonatal fibroblast growth factor-23 (FGF-23) levels are elevated and linked to iron status. Lower fetal iron, indicated by ferritin, is associated with higher FGF-23 in newborns.
Area of Science:
- Endocrinology
- Neonatal Physiology
- Mineral Metabolism
Background:
- Elevated fibroblast growth factor-23 (FGF-23) is linked to skeletal and cardiovascular issues.
- FGF-23 levels are high in neonates, but the underlying mechanisms require further investigation.
- Iron deficiency has emerged as a potential stimulant for FGF-23 production.
Purpose of the Study:
- To investigate the association between fetal iron status and FGF-23 levels in neonates.
- To test the hypothesis that lower cord blood ferritin levels correlate with elevated FGF-23 in newborns.
Main Methods:
- A cross-sectional study involving 64 healthy, full-term neonates.
- Measurements included plasma levels of C-terminal FGF-23 (cFGF-23) and intact FGF-23 (iFGF-23).
- Cord blood ferritin levels were assessed as a marker of fetal iron status.
Main Results:
- Lower cord blood ferritin levels showed a significant association with higher cFGF-23 levels (r = −0.320; P = .014).
- This association remained independent in multivariate analyses, even after adjusting for glycemic indices, maternal race, and parity (B = −0.261, P = .01).
- Higher cord blood glucose and C-peptide levels were also independently linked to elevated cFGF-23.
Conclusions:
- C-terminal FGF-23 (cFGF-23) levels are elevated in the cord blood of healthy term neonates.
- cFGF-23 levels are independently associated with lower serum ferritin and higher glycemic indices in neonates.
- Intact FGF-23 (iFGF-23) levels did not show a significant association with these factors.
Context:
Elevated levels of the phosphate-regulating hormone, fibroblast growth factor-23 (FGF-23) are associated with skeletal and cardiovascular disease. Levels of FGF-23 are elevated in neonates, but the mechanisms are poorly understood. Iron deficiency is a recently described stimulus for FGF-23 production.
Objective:
To test the hypothesis that lower fetal iron status, as measured by lower cord blood ferritin, is independently associated with elevated FGF-23 levels in neonates.
Design And Participants:
This is a cross-sectional study of 64 full-term, healthy neonates.
Setting:
This study took place in a university-based, tertiary care center.
Main Outcome Measures:
Plasma levels of second generation C-terminal FGF-23 (cFGF-23) and intact FGF-23 (iFGF-23).
Results:
Levels of cFGF-23 ranged from 108 to 7508 reference units (RU)/ml (median, 824 RU/ml), and iFGF-23 from undetectable (<8.5) to 135.4 pg/ml (median, <8.5 pg/mL). Ferritin ranged from 58 to 719 ng/ml (mean, 203 ng/ml). Lower cord blood ferritin levels were associated with higher cFGF-23 (r = −0.320; P = .014), but not iFGF-23 levels (r = −0.222; P = .082). In multivariate analyses adjusted for glycemic indices, maternal race, and parity, lower ferritin levels remained independently associated with higher cFGF-23 levels (B = −0.261, P = .01). In the full models, higher cord blood glucose and C-peptide levels were also independently associated with higher cFGF-23 levels.
Conclusions:
cFGF-23, but not iFGF-23 levels, are elevated in cord blood of healthy term neonates and independently associated with lower serum ferritin and higher glycemic indices.
