Abstract
Using a specific vitamin D metabolite assay, the serum levels of various metabolites were measured in 3 children with a history of decreased dietary intake of vitamin D and sun exposure; two had rickets, aminoaciduria and elevated iPTH levels. In some osteomalacic adults, calcitriol levels are said to be normal (Eastwood et al, Lancet i:1377, 1979; Rasmussen, Am J Med 69:360,1980).
Despite reduced 25OH-D levels, calcitriol levels are in the normal range. Nonetheless, the combination of hypocalcemia, hypophosphatemia and increased iPTH should result in even higher calcitriol levels. The ratio of PTH/calcitriol is significantly higher in these patients with reduced 250H-D levels 2.00 vs. 1.06 suggesting actually reduced synthesis of calcitriol in these patients. Non-detection of 24,25OH2D can be explained by high iPTH and low PO4 levels rather than reflecting the inability to synthesize this metabolite. The evaluation of vitamin D deficiency should include the measurement of all metabolites.
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Chesney, R., Zimmerman, J., Hamstra, A. et al. 392 THE CIRCULATING LEVELS OF VITAMIN D METABOLITES IN VITAMIN D DEFICIENCY: THE MEANING OF NORMAL CALCITRIOL (l,250H2-VITAMIN D) LEVELS. Pediatr Res 15 (Suppl 4), 505 (1981). https://doi.org/10.1203/00006450-198104001-00403
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DOI: https://doi.org/10.1203/00006450-198104001-00403