Abstract
To explore the temporal evolution of 25-hydroxyvitamin D [25(OH)D], its epimer, parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), and minerals in healthy appropriate-for-gestational-age preterms.
A prospective study was undertaken in infants born at 28–32 weeks with monitoring at 1, 3, 5 weeks and term.
Morning plasma and urine calcium; phosphorus; creatinine; PTH, C-terminal and intact FGF23 (iFGF23) and liquid chromatography-tandem mass spectrometry measurements of 25(OH)D were undertaken. Analyses included regression models.
Some 11 infants (5 males) were recruited at a median gestational age of 31.2 weeks (interquartile range: 28.1–31.8). Standard chemistries were normal. No infant was vitamin D deficient; 58% achieved 50 nmol/L with a median intake of 540 IU/day. High concentrations of C-3 epimer were detected. iFGF23 and C-terminal concentrations were persistently elevated (double and ten times adult norms, respectively). Tubular resorption of phosphorus was normal (88%±8%).
Most infants achieved acceptable 25(OH)D
concentrations. The biologic significance of the elevated FGF23 is unclear.