INTRODUCTION: Parathyroid hormone (PTH) and vitamin D are essential hormones in bone metabolism, especially during pediatric growth. Vitamin D insufficiency is often asymptomatic and is prevalent in high-latitude countries.

METHODS: In a Danish population-based cohort of 2,211 6-18-year-olds, sex- and age-specific pediatric reference values for fasting concentrations of intact serum PTH, vitamin D (25-hydroxycholecalciferol, 25-OH-D), total calcium, and phosphate were generated in accordance with Clinical and Laboratory Standards Institute (CLSI) EP28-A3c guidelines. The effect of season on these biomarkers of bone metabolism was evaluated.

RESULTS: In boys, PTH concentrations increased with age, while the vitamin D and phosphate concentrations decreased (all p<.001). In girls, a peak in PTH concentrations and a nadir in vitamin D concentrations were observed in the 10-14-year-olds (both p<.001). Calcium and phosphate decreased with age for both sexes (girls: both p<.001; boys calcium: p<.05, boys phosphate: p<.001). Vitamin D was 20% lower in winter than summer for both sexes (both p<.001). Individuals with vitamin D sufficiency (25-OH-D >50 nmol/L) exhibited a 5% lower level of PTH compared to the whole sample population (p<.001).

CONCLUSION: The concentrations of PTH, vitamin D, calcium, and phosphate vary during childhood and adolescence, and is dependent on sex and season. These factors should be considered when screening for and treating imbalances in bone metabolism.