To determine the
biological criteria for neonatal
vitamin D deficiency, serum
25-hydroxyvitamin D (
calcidiol),
parathyroid hormone (PTH),
calcium, phosphates, and
alkaline phosphatase (ALP) activity were measured during the winter-spring period in 80 healthy neonates and their mothers 3-6 d after delivery. A longitudinal 3-mo survey of the serum biology of 52 of these neonates consuming formula was also performed to test the influence of their neonatal
vitamin D status on the effects of two oral
ergocalciferol supplements (500 and 1000 IU or 12.5 and 25 micrograms/d). At birth, 63.7% of the infants had
calcidiol concentrations < or = 30 nmol/L. Most of them had no other
biological sign evocative of
vitamin D deficiency, but 14 neonates had low
calcidiol concentrations and serum PTH concentrations > 60 ng/L, the upper limit of the adult normal range. They also had a significantly lower mean serum
calcium concentration than did neonates with
calcidiol concentrations > 30 nmol/L. On the basis of the association of low
calcidiol concentrations (< or = 30 nmol/L) and high PTH concentrations (> 60 ng/L) as criteria for
vitamin D deficiency, 24% of the neonates born to unsupplemented mothers were found to be
vitamin D-deficient. Neonatal
vitamin D status influenced the response of the infants to
vitamin D supplements. Neonates with no sign of
vitamin D deficiency showed similar changes in their serum
calcidiol,
calcium, phosphate, and PTH concentrations and ALP activity and no toxic effect (
hypercalcemia or highly elevated
calcidiol concentration) was observed whatever their
vitamin D intake. In contrast, neonates with subclinical
vitamin D deficiency had normalized serum PTH within 1 mo only when they were given 1000 IU
ergocalciferol (25 micrograms)/d in addition to their formula.