Object: Adolescence is the period during which the greatest accrual of bone mineral occurs. During puberty, changes of bone metabolism primarily depend on maturity. Diagnosis and therapy of childhood bone diseases is difficult due to the lack of reference ranges of metabolic bone markers. Our aim was to establish the reference values of bone markers in primary school students (mean age: 13.2±1.2 years; 65 girls, 56 boys).
Methods: The children were divided into two groups: prepubertal (boys:22, girls:38) and pubertal (boys:34, girls:27). This classification was based on the Tanner stage and levels of serum sexual steroids (testosteron, estradiol). Physical activity, dietary habits, calcium intake, consumption of soft drinks and body mass index (BMI) was established. Bone mineral density (BMD), bone mineral content (BMC), vertebral Z-score (DEXA Medical Systems Prodigy), and serum biochemical markers (osteocalcin: OC; beta-crosslaps: βCL; procollagen type I N-terminal propeptid: P1NP) were measured by an electrochemiluminescence immunoassay system (ECLIA, Elecsys 2010, Roche). The data were analysed in terms of sexual maturation by one way ANOVA.
Results: The Tanner stage (3.14±0.78) and BMD (0.99±0.14) values of girls were significantly higher than those in boys (Tanner stage: 2.75±0.61, BMD:0.87±0.12). A significant (P<0.001) positive correlation (r=0.40.5) was observed between the Tanner stage and the parameters of mineral density (BMD, BMC, Z-score). Significantly (P<0.001) higher OC (190±66 vs. 139±61 ng/ml) P1NP (838±280 vs 569±360 ng/ml), βCL (2.03±0.65 vs. 1.50±0.60 ng/ml) values were measured in boys than in girls. Boys not consuming soft-drinks regularly exhibited significantly higher (P<0.05) prepubertal Z-score values (+0.28±0.77) that regular soft-drink-consumer boys (−0.72±1.02). iPTH levels in soft drink-consuming prepubertal girls (47.7±13.6) were significantly higher (P<0,01) than in the non-consuming prepubertal girls (32.8±9.4 ng/ml).
Conclusion: The results call the attention on the significance of appropriate reference ranges. It is advisable that boys and girls are evaluated separately with the sexual maturity taken into consideration. The assessment of dietary habits strongly suggests insufficient spontaneous calcium intake among children.