Vitamin D, bone density, and nephrocalcinosis in preterm infants: a prospective study

High Initial Dose of Monitored Vitamin D Supplementation in Preterm Infants (HIDVID Trial): Study Protocol for a Randomized Controlled Study

Vitamin D deficiency can escalate prematurity bone disease in preterm infants and negatively influence their immature immunology system. Infants born at 24 + 0/7 weeks to 32 + 6/7 weeks of gestation will be considered for inclusion. Cord or vein blood samples will be obtained within 48 h after birth for 25-hydroxyvitamin D level measurements. Parathyroid hormone and interleukin-6 levels will be measured. Infants will be randomized to the monitored group (i.e., an initial dose of 1000 IU/day and possible modification) or the controlled group (i.e., 250 IU/day or 500 IU/day dose, depending on weight). Supplementation will be monitored up to a postconceptional age of 35 weeks. The primary endpoint is the percentage of infants with deficient or suboptimal 25-hydroxyvitamin D levels at 28 ± 2 days of age. 25-Hydroxyvitamin D levels will be measured at postconceptional age 35 ± 2 weeks. Secondary goals encompass assessing the occurrence of sepsis, osteopenia, hyperparathyroidism, and interleukin-6 concentration. The aim of this study is to evaluate the efficacy of monitored vitamin D supplementation in a group of preterm infants and ascertain if a high initial dosage of monitored vitamin D supplementation can decrease the occurrence of neonatal sepsis and metabolic bone disease.

Nephrocalcinosis in Neonates

Nephrocalcinosis occurs in as many as 40% of preterm neonates. Many causes and contributors predispose neonates to develop nephrocalcinosis, including metabolic, genetic, and iatrogenic factors. Because nephrocalcinosis can be a manifestation of an underlying genetic disorder, neonates with nephrocalcinosis must undergo an evaluation to identify and address contributors, to prevent further renal calcium deposition that can potentially lead to renal dysfunction. In this article, we review the epidemiology, pathogenesis, diagnosis, and evaluation of nephrocalcinosis in neonates. We also summarize the natural history of nephrocalcinosis of prematurity as well as the management of this condition.

Tibial quantitative ultrasound compared to dual-energy X-ray absorptiometry in preterm infants

OBJECTIVE

The gold standard for diagnosing metabolic bone disease in pediatrics is dual-energy x-ray absorptiometry (DXA). Bone quantitative ultrasound (QUS) has increasing applications. This study compared the relationship of DXA to QUS in preterm infants.

DESIGN

Prospective observational study of preterm infants ≤32 weeks gestation or ≤1800 grams at birth. DXA scans measuring bone mineral content (BMC) and tibial QUS scans measuring bone speed of sound (SOS) were obtained near term gestation.

RESULTS

41 infants had bone scans at mean corrected gestation 37.7 ± 2.1 weeks. BMC and SOS showed weak inverse correlation (R² 0.163, p < 0.01). BMC and SOS correlated with parameters at corrected gestational age at the time of the bone scans (p < 0.05-0.001). SOS correlated with birth gestational age (p < 0.001), not BMC.

CONCLUSIONS

A statistically significant weak inverse correlation between DXA and QUS was observed. QUS may have advantages over DXA.