Bone turnover markers in the obese children – relation to gender, body composition and leptin level

Introduction. Recently published data revealed that bone turnover is related to the body composition in pubertal children and may be impaired in obese adolescents. The aim of the study was to determine the relationship between bone turnover markers, body composition and leptin level in obese children. Material and methods. In 54 obese adolescents (25 boys and 29 girls) in the mean age of 13.96 ±2.78 years bone turnover markers – osteocalcin (OC), N-terminal telopeptide of type I collagen (NTx), OC/NTx ratio and leptin were determined. Anthropometric parameters expressed as BMI Z-score, WHR, W/HtR and body composition was evaluated by bioelectrical impedance analysis (BIA)such as fat mass (FAT), fat-free mass (FMM), predicted muscle mass (PMM) and total body water (TBW). The results were compared to the control group of 75 normal weight children (25 boys and 38 girls). Results. OC was significantly lower in obese children, particularly in obese girls (p<0.05 and p<0.0001 respectively). Bone turnover ratio (calculated as OC/NTx) was significantly lower in obese girls only (p<0.01). Significant negative correlation was found between the OC level and BMI Z-score in the whole studied population of children. OC and OC/NTx correlated significantly with all anthropometrical parameters only in girls. There was also a significant positive correlation between NTx and leptin in the entire group, being significantly higher in females (p<0.05 and p<0.0001 respectively). Conclusions. Bone turnover is related to the amount of fat mass and its hormonal activity. We can suspect that, in obese children, particularly in obese adolescent girls, impairment of bone turnover may be a risk factor for the lower bone mass and higher fracture risk in the future life