Metabolism of Vitamin D₃-³H in Vitamin D-Resistant Rickets and Familial Hypophosphatemia

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Abstract

The fate of an intravenous dose of tritiated vitamin D3 was studied in seven normal subjects, four children with vitamin D-resistant rickets, and four adults with a familial history of vitamin D-resistant rickets and persistent hypophosphatemia. An abnormal metabolism of vitamin D in vitamin D-resistant rickets was defined and characterized by a decrease in the plasma fractional turnover rate, a marked increase in plasma water-soluble metabolites, and a relative decrease in the conversion of vitamin D to a polar, biologically active metabolite. Alterations in vitamin D metabolism in the adults with persistent hypophosphatemia were similar but less severe than those of affected children with vitamin D-resistant rickets. It is tentatively concluded that the abnormalities in vitamin D metabolism documented in patients with vitamin D-resistant rickets and familial hypophosphatemia may account for the observed osseous and biochemical changes.

Authors

Louis V. Avioli, T. Franklin Williams, Judith Lund, Hector F. DeLuca