The aim of the study was to evaluate the bone-optimal pediatric levels of 25-hydroxy-vitamin D (25OHD) by testing the level at which 25OHD optimally effects calcium, phosphorus, and parathyroid hormone levels in a large population-based dataset. This was an observational retrospective "big-data" study. We analyzed 49 935 25OHD tests from children sampled in Clalit Health Services, Jerusalem district between 2009 and 2019. Associated data were available in the following number of samples: corrected calcium; 18 869, phosphorus: 1241, and PTH: 449. We tested correlations between each parameter and 25OHD, adjusting phosphorus levels by age using a "phosphorus index". Pearson's and Spearman's correlation coefficients were calculated to determine the strength of the correlation between 25OHD and each parameter. There was a significant correlation between 25OHD levels and both PTH and calcium but not for the phosphorus index. The level at which increase in 25OHD continued to cause significant alteration was: for PTH up to 100 nmol/l (40 ng/ml), for corrected calcium it increased beyond 100 nmol/l. Increasing levels of 25OHD levels up to at least 100 nmol/l are associated with improvement in parameters known to be associated with increased bone mineralization. Therefore, one should aim for a 25OHD level of 100 nmo/l.
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