Breast milk intake, intact parathyroid hormone, and %tubular phosphate reabsorption as predictors of bone mineral density at term-equivalent age in very preterm and/or low-birth-weight infants: A prospective cohort study.

BACKGROUND

Predicting and preventing metabolic bone disease (MBD) in preterm infants remains challenging.

AIMS: To evaluate the associations of bone mineral density (BMD) with fortified breast milk intake, and biochemical markers, including intact parathyroid hormone (iPTH), and %tubular phosphate reabsorption (%TRP).

STUDY

DESIGN

A prospective observational study conducted at a single tertiary center in Japan.

SUBJECTS: Infants born at ≤31 weeks of gestation and/or birth weight ≤ 1500 g from August 2018 to August 2020.

OUTCOME MEASURES: Cord blood iPTH and 25-hydroxyvitamin D, weekly serum iPTH, alkaline phosphatase (ALP), and %TRP were measured until term-equivalent age (TEA). BMD at TEA was assessed using dual-energy X-ray absorptiometry. Associations between clinical and biochemical variables and BMD were analyzed.

RESULTS

Of 137 infants screened, 105 were included in the analysis. Higher breast milk intake was positively correlated with BMD, whereas elevated iPTH levels and lower %TRP at 3-8 weeks were negatively correlated with BMD. In multivariable regression analysis, birth weight and breast milk intake were positively correlated with BMD, whereas iPTH levels at 4 weeks were negatively associated. A linear mixed-effects model confirmed this longitudinal association. Gestational age, ALP, and 25-hydroxyvitamin D levels were not associated with BMD.

CONCLUSION

Lower breast milk intake and elevated iPTH levels are indicators of reduced BMD at TEA in very preterm and very-low-birth-weight infants. %TRP may serve as a practical alternative marker, when iPTH measurements are unavailable. Early monitoring of iPTH and/or %TRP, combined with optimized fortified breast milk intake, may support bone health in this high-risk population.