American Journal of Clinical Nutrition, Vol 22, 448-457, Copyright © 1969 by The American Society for Clinical Nutrition, Inc.

Vitamin D-Resistant Rickets and High Fecal Endogenous Calcium Output

A Report of Two Cases

¹ From the University of Louisville School of Medicine, Louisville, Kentucky 40202

Combined balance and radiocalcium kinetic studies were carried out in two children with vitamin D-resistant rickets during vitamin D therapy (50,000 U/day), and again 8 weeks after vitamin withdrawal. These studies showed: 1) high fecal endogenous calcium excretion, which was slightly aggravated by vitamin D withdrawal; 2) apparently normal intestinal calcium absorption, which was not enhanced by vitamin D therapy; and 3) markedly increased bone-calcium turnover rates following vitamin D withdrawal.

High fecal endogenous calcium loss and unresponsiveness of gastrointestinal absorption of calcium to vitamin D are suggested as the primary defects in these two cases. In the absence of any demonstrable increase in the net absorption of calcium from the gastrointestinal tract, the diminution of bone turnover and the increased urinary calcium excretion observed during vitamin D therapy are interpreted as direct effects of the vitamin.

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