Cut off Value for Parathormone Level in Children with Vitamin D Deficiency

Background: When serum level of 25-hydroxy vitamin D [25(OH) D] decreases, intact Parathormone (iPTH) level increases compensatory. This study aimed to determine the cut off value for iPTH level in 2-14-year-old children with vitamin D (VD) deficiency. Methods: This cross-sectional study was performed on 153 children aged 2-14 years old who referred to the endocrinology clinic of Amirkola Children's Hospital for growth assessment. Census sampling was conducted from January 2016 to June 2017 according to the eligibility criteria including height and weight above the percentile of 3% of growth charts and normal serum of calcium level (>8.5 mg/dl). Laboratory parameters such as serum calcium, 25(OH) D and iPTH levels were assessed. The children were divided into three groups based on serum levels of 25(OH) D as mild, moderate and severe VD deficiency. The Receiver Operating Characteristic (ROC) curve was used to analyze the cut-off point of iPTH and 25(OH) D. P-Value< 0.05 was considered significant. Results: The mean VD and iPTH levels in children were 11.8 ± 4.59 ng/ml and 28.3 ± 13.3 pg/ml, respectively. At the iPTH serum level of 23.5 pg/ml, with a sensitivity of 66.1%, there was a possibility of moderate to severe VD deficiency. In the severe deficiency group, at the iPTH serum level of 23.5 pg/ml and above, with a sensitivity of 78.9%, there was a possibility of severe VD deficiency. The cut-off point of 25(OH) D and iPTH, at the serum VD level ≤10 ng/ml were determined. Conclusions: The results of the present study showed that the cut-off value for iPTH in children with VD deficiency is serum level of 25OHD≤10ng/ml