Serum 25-hydroxyvitamin D levels and its relationship with sex hormones, puberty and obesity degree in children and adolescents

ABSTRACT Background/objectives Puberty and obesity have been associated with vitamin D deficiency but there is a lack of studies assessing this triple relationship at once. Thus, the aim of this study was to evaluate, under a cross-sectional design, the relationship between sex hormone levels and serum 25-hydroxyvitamin D (25(OH)D), taking into account pubertal status and obesity degree. Subjects/methods A total of 460 participants from the GENOBOX study (241 females), aged 6–18 years were included in the analysis. Children were divided in groups according to their pubertal stage (prepubertal (n = 225) and pubertal (n = 235)) and obesity degree (normal weight children (n = 100) and children with overweight/obesity (n = 360)). Serum 25(OH)D, Follicle-Stimulating Hormone (FSH) and Luteinizing hormone (LH), estradiol and testosterone were measured. 25(OH)D levels were categorized and the hormones concentration wasadjusted by sex and converted into tertiles. Mann Whitney and Kruskal–Wallis tests, and quantile regression were performed. Results Pubertal children showed lower serum concentrations of 25(OH)D than prepubertal children (median: 20 ng/mL vs. 24 ng/mL, respectively; p = 0.006). Moreover, within normal weight children, differences were found for 25(OH)D levels according to tertiles of testosterone (I: 27 ng/mL; II: 30 ng/mL; III: 19 ng/mL, p = 0.008). Among overweight/obese, differences were found according to the tertiles of FSH (I: 25 ng/mL; II: 21 ng/mL; III: 19 ng/mL, p = 0.010), LH (I: 24 ng/mL; II: 21 ng/mL; III: 20 ng/mL, p = 0.004) and estradiol (I: 24 ng/mL; II: 21 ng/mL; III: 19.5 ng/mL, p = 0.043). Finally, higher concentrations of FSH were associated with a reduction of 25(OH)D levels in children with overweight/obesity (coefficient: −1.092, p = 0.022). Conclusion Higher concentrations of sex hormones (FSH, LH, and estradiol) were associated with lower 25(OH)D levels in children with overweight or obesity. Thus, pubertal status and obesity degree need to be considered to achieve an optimal status of vitamin D in children.