Serum 25-hydroxyvitamin D (25-OH-D) in obese adolescents

Background: There is increasing evidence that vitamin D deficiency is common and has been associated with several non-bone related outcomes, including insulin resistance, type 2 diabetes and cardiovascular disease. The influences of gender, puberty, and adiposity on serum hydroxyvitamin D (25-OH-D) levels and the relationship between 25-OH-D and insulin resistance in obese children were studied. Material and methods: Age, gender, pubertal stage, weight status (standard deviation score of body mass index: BMI-SDS, percentage body fat, waist circumference), 25-OH-D levels, and insulin resistance index calculated by homeostasis model assessment (HOMA-IR) were evaluated in 64 obese adolescents. Multivariable linear regression was used to determine factors associated with decreased serum 25-OH-D levels and to study the relationship between 25-OH-D and HOMA-IR. Results: Median serum 25-OH-D level was 10.1 ng/mL (25.2 nmol/L). 14 % of patients were vitamin D-sufficient (25-OH-D ≥ 20 ng/mL), 36 % had intermediate values (11–19 ng/mL), and 50 % were deficient (25-OH-D ≤ 10 ng/mL). In the multivariable model, older age, pu-berty, higher value of percentage of body fat, and the presence of acanthosis nigricans (AN) were all negatively associated with 25-OH-D. Lower 25-OH-D levels were also associated with higher blood glucose, insulin and HOMA-IR after adjustment for puberty and SDS-BMI. Summer positively correlated with 25-OH-D level. Conclusion: Our study confirms that obesity is a risk factor for vitamin D deficiency. Hypovitaminosis D, common in obese adolescent