Vitamin D Deficiency and Its Cut-off Point among Young Teenagers

Vitamin D has a basic role in bone development and metabolism. Regarding high prevalence of vitamin D deficiency in Iran, we aimed to investigate its point prevalence in Arak, Iran and determine a cut-off point for vitamin D deficiency in the region. In a cross-sectional study,420 adolescents (220 girls, 200 boys) aged 10-16 years old were selected using a multistage sampling. Plasma level of vitamin D and PTH were evaluated using radio immune assay and immuno radio metric assay, respectively. The relation between vitamin D and PTH was assessed through scatter diagram and the cut-off points for vitamin D deficiency were detected accordingly. The prevalence of vitamin D deficiency in different cut-off points, as well as, the associated factors were analyzed using SPSS 15.00. Student t-test was used to compare the girls and the boys. Considering 25(OH) vit-D level <20 ng/ml as vitamin D deficiency, 84% of the students were vitamin D deficient (99.1% of girls, 66.5% of boys) (P=0.001). Scatter diagram showed three cut-off points for vitamin D deficiency as 25(OH) vit-D level < 13, 21, 33 ng/ml. Vitamin D deficiency is more prevalent among girls than boys and increases with increased weight (P=0.05). A cut-off point of 25(OH) vit-D <13 ng/ml is recommended for detecting vitamin D deficiency in Arak, Iran.