Endocrine Abstracts

Objective: Obesity and vitamin D deficiency are become most important public health problems independently. We aimed to investigate the relationship between vitamin D levels and metabolic sydrome (MetS) in obese children and adolescents.

Patients and methods: 51 obese children/adolescents at the age of 12.4±2.73 (7.0–18.0) years and 48 age–sex matched healthy controls were enrolled. Serum 25 OHD, 1,25 (OH)2 D, calcium, phosphorus, alkaline phosphatase, parathormone (PTH) were measured in all participants. Vitamin D sufficiency, insufficiency and deficiency were defined as serum 25 OHD concentrations >20 ng/ml, <20 ng/ml, <15 ng/ml, respectively. IDF, NCEP ATP III and WHO criterias were used to describe MetS.

Results: 2% severe deficiency, 35.3% deficiency, 23.5% insufficiency and 39.2% sufficiency of vitamin D was found in the obese group. The serum concentration of 25 OHD was 18.2±6.2 ng/ml, 1,25 (OH)2 D was 28.9±11.7 pg/dl in the obese group, and 25.6±5.9 ng/ml, 25.5±9.3 pg/dl in control group, respectively. Obese children demonstrated significantly decreased 25 OHD levels compared to control group; however their 1,25 (OH)2 D and parathormone levels were similar. Cut-off level for 25 OHD which lead to increased PTH was found 15.8 ng/ml (specificity 53.5%, sensitivity 72.5%) by ROC analysis. Also, at the cut-off level of 13.6 ng/ml for 25 OHD, specificity increased to 72.5% and sensitivity increased to 81%. There was no association between serum 25 OHD, 1,25 (OH)2 D and MetS.

Conclusions: Obese children demonstrated significantly decreased 25 OHD levels, while their 1,25 (OH)2 D and PTH concentrations were similar with healthy controls. Therefore, we speculated that it was not suitable to detect serum 25 OHD - as it is stored in adipose tissue- in obese children. New methodologies for detecting 25 OHD levels and new detailed studies to determine a new cut- off level for vitamin D deficiency in obese children are needed.