Kidney Week

Abstract: PUB210

Calcium, Phosphorus, and Vitamin D Metabolism in the First Year of Life: A Prospective Study

Session Information

• Publication Only

Category: Pediatric Nephrology

• 1800 Pediatric Nephrology

Authors

• Gurevich, Evgenia, Barzilai Medical Center, Ashkelon, Israel

Evgenia Gurevich, MD

• Alktnani, Noha, Barzilai Medical Center, Ashkelon, South District, Israel

Noha Alktnani

• Akirav, Nofar, Barzilai Medical Center, Ashkelon, South District, Israel

Nofar Akirav

• Aharoni, Dorit, Barzilai Medical Center, Ashkelon, Israel

Dorit Aharoni, PhD

• Arazi, Eden, Ben Gurion University of Negev, Beer Sheva, Israel

Eden Arazi, PhD

• Segev, Yael, Ben Gurion University of Negev, Beer Sheva, Israel

Yael Segev, PhD

• Landau, Daniel, Schneider Children's Medical Center of Israel, Petah Tikva, Center District, Israel

Daniel Landau, MD

Background

Calcium (Ca) and phosphorus (Pi) are essential for normal bone growth and are tightly regulated. Fetal (placenta centered) regulation differs from postnatal (intestine and kidneys oriented), and this balance must change after birth to enable continued intensive growth. We aimed to investigate early Ca, Pi and vitamin D metabolism in healthy infants.

Methods

We prospectively evaluated healthy neonates and infants (age 0-12 months), admitted for non-infectious reasons between 12\2023-09\2025, and assessed blood and urinary Ca and Pi, serum PTH and vitamin D active and inactive metabolites.

Results

Nineteen infants were recruited, 14 (74%) of them were males. Median (IQR) age was 2.6 (0.2, 2.9) months. Four of them (21%) were exclusively breast fed, 6 (32%)-formula fed, and 9 (47%) received mixed nutrition. Mean (±SD) serum Ca, Pi, PTH were within the normal range: 10.4±0.5 mg/dl, 6.5±0.9 mg/dl, and 22.9±8.1 pg/ml, respectively. None of the patients had hypercalciuria. Tubular reabsorption of phosphate (TRP) was high (95.5±5.4%), reflecting low FGF23 activity. Mean serum levels of 25(OH)D were around normal values [22.8±11.7 ng/ml (N>20)], 1,25(OH)₂D levels were high [341±141 pg/ml (N+40-120)], and 24,25(OH)₂D were low [1.2±1.1 ng/ml (N=1.8±0.6)]. Median [25(OH)D]-to-[24,25(OH)₂D] ratio, wich reflects CYP24A1 activity, was 29.9 (IQR 14.4,35.8), and in 10 (51%) cases it exceeded the upper limit of norm (N=7-23). Serum 24,25(OH)₂D had strong positive correlation with age (R² = 0.8) (Fig 1).

Conclusion

In healthy newborns and infants low CYP24A1 and FGF23 activity lead to high levels of active vitamin D metabolite, which enables the maintenance of blood Ca and Pi levels appropriate for rapid skeletal growth. If these preliminary data are confirmed by larger studies, a re-evaluation of the need for vitamin D supplementation in healthy infants could be offered.