Circulating Total Osteocalcin Reflects Bone Mineral Physiology Rather than Metabolic Risk in Pediatric Obesity

Background: Osteocalcin is a bone-derived protein traditionally regarded as a marker of bone formation, but experimental and clinical studies have suggested potential endocrine effects on energy and glucose metabolism. In pediatric populations, particularly in the context of obesity, the relationships between circulating osteocalcin, adiposity, and metabolic health remain inconsistent and poorly defined. Objective: To investigate associations between serum total osteocalcin and anthropometric, metabolic, biochemical, and body composition parameters in children and adolescents with obesity, with particular emphasis on adiposity and mineral metabolism. Methods: This retrospective cross-sectional study included 155 children and adolescents aged 4-18 years with obesity. Anthropometric measurements, laboratory parameters, and body composition assessed by dual-energy X-ray absorptiometry were extracted from medical records. Associations between osteocalcin z-scores and clinical variables were evaluated using linear regression models. Multivariable and extended regression models were applied to assess independent associations. Results: Osteocalcin was positively associated with markers of mineral metabolism, including serum 25-hydroxyvitamin D₃ (β = 0.19, p = 0.012), serum calcium (β = 0.19, p = 0.015), and free triiodothyronine (β = 0.32, p < 0.001) in multivariable analyses. No independent associations were observed between osteocalcin and measures of adiposity, including body mass index, visceral adipose tissue index, leptin, or markers of glucose and lipid metabolism. Conclusions: In children and adolescents with obesity, circulating osteocalcin is primarily associated with mineral metabolism rather than adiposity or metabolic health. These findings support the interpretation of total osteocalcin as a clinically accessible marker of bone turnover and mineral homeostasis rather than a robust surrogate of metabolic dysfunction in pediatric obesity.