Effects of Hypervitaminosis a and D on Skeletal Metabolism.

The feeding of escessive amounts of vitamin D to animals causes pathological changes in the skeleton and calcification of soft tissues (l-4). Hypervitaminosis A causes bone fragility. Spontaneous fractures occur in growing rats, whereas in the adult rat only rarefaction develops (5-8). Although excesses of each vitamin cause specific pathological changes, the concomitant feeding of toxic amounts of both vitamins prevents to a large extent soft tissue calcification and the skeletal changes that accompany hypervitaminosis D (g-10). The present investigation was undertaken to determine how vitamin A exerts its beneficial action in offsetting some of the pathological changes observed in hypervitaminosis D. A preliminary account of these studies has been reported (1 I).