The Correlation Between Serum 25-Hydroxyvitamin D and Parathyroid Hormone Levels and Orthostatic Intolerance in Children

Abstract Background: To investigate the correlation between orthostatic intolerance (OI) and serum 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone (PTH) levels in children.Methods: This study reviewed 151 children who were first admitted to the Lanzhou University Second Hospital (LZUSH) between January 2019 and August 2020 and were eventually diagnosed with OI. There were 142 children with OI, including 93 children with vasovagal syncope (VVS), 45 children with postural orthostatic tachycardia syndrome (POTS) and 4 children with orthostatic hypotension (OHT). Eighty-seven children who visited the Child Health Management Center of LZUSH in the same period were selected as healthy control. All children were examined for 25 hydroxyvitamin D and parathyroid hormone at the first visit.Results: 1. Compared with healthy children, serum 25(OH)D level was significantly decreased in OI children (P<0.001), but there was no difference in PTH level (P= 0.161). 2. Binary logistic regression analysis showed that the level of 25(OH)D was the only factor causing OI. Every unit of 25(OH)D increased, the probability of OI decreased by 74.7%（95%CI: 0.177-0.328）. 3. The sensitivity and specificity of 25(OH)D for the diagnosis of OI were 93.7% and 64.4%, respectively, with the threshold value of 19.5ng/L. Conclusion: The 25(OH)D level of the patients with OI was significantly decreased. Taking serum 25(OH)D concentration of 19.5ng/ml as the critical value may be useful for the diagnosis of OI.