Phosphate concentrations and modifying factors in healthy ch
Phosphate homeostasis and its modifiers in early childhood are inadequately characterized.

This study aimed to determine physiological plasma phosphate concentration and modifying factors in healthy infants at 12 to 24 months of age.

This study included 525 healthy infants (53% girls), who participated in a randomized vitamin D intervention (VIDI) trial and received daily vitamin D3 supplementation of either 10 or 30 µg from age two weeks to 24 months. Biochemical parameters were measured at 12 and 24 months. Dietary phosphate intake was determined at 12 months.

-- Mean (SD) phosphate concentration decreased from 12 months (1.9±0.15 mmol/L) to 24 months (1.6±0.17 mmol/L) of age.

-- When adjusted by covariates, such as body size, creatinine, 25OHD, intact and C-terminal FGF23, mean plasma phosphate was higher in boys than girls during follow-up.

-- Phosphate concentrations were similar in the vitamin D intervention groups.

-- Plasma iron was associated positively with plasma phosphate at both time points.

-- At 24 months of age, the main modifier of phosphate concentration was plasma creatinine.

Conclusively, plasma phosphate concentration decreased from age 12 to 24 months. In infants and toddlers, the strongest plasma phosphate modifiers were sex, iron, and creatinine, whereas vitamin D supplementation did not modify phosphate concentrations.