The Production of Hypercalcemia with Small Amounts of Vitamin D

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Abstract
The inclusion of one I.U. of vitamin D per gram in a diet very low in phosphorus and high in calcium produced a pronounced hypercalcemia in rats. Irradiated ergosterol, pure calciferol, or irradiated 7-dehydrocholesterol were equally effective, whereas dihydrotachysterol (A.T.-10) was much less effective. The degree of hypercalcemia produced by vitamin D was found to be dependent on the amount of calcium in the diet. Growth was inhibited only in those animals in which there was a rather marked hypercalcemia. In general, the extent to which growth was inhibited was directly related to the degree of hypercalcemia. Calcification, as judged by either the absolute or relative amounts of femur ash, was greater in those cases in which there was a definitive increase in serum calcium. These data (1)give additional evidence in favor of the view that vitamin D increases the absorption of calcium from the intestines, and(2)serve to emphasize the importance of the calcium-phosphorus product of the serum in calcification.