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Bone Abstracts (2013) 2 P61 | DOI: 10.1530/boneabs.2.P61

ICCBH2013 Poster Presentations (1) (201 abstracts)

Elevated FGF23 levels in premature infants without excessive phosphaturia

Tarah Fatani , Asma Binjab , Hope Weiler , Atul Sharma & Celia Rodd


McGill University, Montreal, Quebec, Canada.


Preterm infants develop reduced bone mass and fragility fractures. Nevertheless, normal ranges in preterm infants are poorly defined for concentrations of vitamin D; its isomers (C3α-epimer of 25(OH)D3) and metabolites (24, 25(OH)2D3, 1, 24(OH)2D); and other mineral-regulating hormones, including FGF23 in both intact (iFRG23) and inactive (C- terminal) forms.

Objective: To clarify normal concentrations of minerals and hormones in healthy, preterm infants (AGA).

Methods: We conducted a longitudinal, pilot, cohort study on infants born at 28–32 weeks gestation, monitoring blood and urine at 1, 3, and 5 weeks and at term. Analyses included morning plasma and urine calcium, phosphorus, creatinine (Beckman Coulter, USA), whole blood ionized calcium (Radiometer, Denmark), PTH, cFGF23 (C-terminal and intact; Immunotopics, USA), iFGF23 (Kainos, Japan), 1, 25(OH)2D (IDS, UK) and 25(OH)D3 and its C3α-epimer and metabolites by LC–MS/MS (Warnex, Canada). Data are mean±S.D.

Results: Eleven infants (mean GA 30.9±1.5 weeks, wt 1866±21.6 g, male=5) were recruited. At weeks 1, 3, 5, and term, the % achieving 50 nM concentrations of 25(OH)D3 were 40, 60, 100, and 67%, with good intakes of vitamin D. Levels of iFGF23 were mildly elevated (double adult norms) with a marked increase in cFGF23 (ten times adult norms). Nevertheless, tubular resorption of phosphorus (TRP) was normal (88±8%) for those with urine samples. Preterm infants had substantial concentrations of C3α-epimer, much higher than in adults. Calcitriol levels were robust at all ages.

Table 1 Results of blood biochemistry and hormone concentrations across time in preterm infants.
WeeksIonized calcium (mM)Phos (mM)iFGF23 (pg/ml)cFGF23 (RU/ml)25(OH)D3 (nM)C3α epimer (%)PTH (pM)1,25(OH)2D (pM)
1 (n=10)1.39±0.052.26±0.568.2±59.9839±49454.3±21.032.4±5.76.0±5.0213.0*
2 (n=10)1.42±0.052.23±0.2671.7±31.6737±35557.1±25.743.4±6.76.0±3.2134.7±40.5^
5 (n=2)1.41±0.022.17±0.1395.5±3.5888±8053±3.949. 9±14.85.7±1.8185.0±53.3^
Term (n=7)1.40±0.032.35±0.2075.8±22.71060±39762.2±21.147.7±13.63.2±1.9224.0*
*n=1, n=3.

Conclusions: Many infants achieved acceptable 25(OH)D3 concentrations. Despite elevated concentrations of FGF23, there was not excessive phoshaturia.

Volume 2

6th International Conference on Children's Bone Health

Rotterdam, The Netherlands
22 Jun 2013 - 25 Jun 2013

ICCBH 

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