THE EFFECT OF VITAMIN D ON CALCIUM AND PHOSPHORUS METABOLISM; STUDIES ON FOUR PATIENTS

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Abstract
1. Metabolic studies were performed on 4 patients. Patient 1 was under treatment for a form of rickets very resistant but not intractable to vit. D therapy; Patients 2, 3, and 4 had idiopathic hypoparathyroidism. 2. An increase in the ingested Ca in Patient 1 was followed by an increase in the fecal P excretion; however, an increase in the phosphate ingested was not followed by an increase in the fecal Ca excretion. Ca in the diet evidently has more influence on phosphate absorption than phosphate in the diet has on Ca absorption. 3. The intraven. intake of large amts. of phosphates in Patient 1 was followed by no increase in the fecal excretion of phosphate; reexcretion of phosphate into the gastro-intestinal tract was not influenced by the amt. of phosphate entering the blood. When the same amt. of phosphate was given by mouth, there was likewise no increase in the fecal phosphorus excretion. The amt. of phosphate in the feces evidently was independent of the amt. of phosphate ingested. Large amts. of vit. D, however, decreased the fecal phosphorus excretion as well as the fecal Ca excretion; the fecal phosphorus excretion depends on the fecal Ca excretion and vit. D decreased the latter. 4. Vitamin D therapy in Patient 1, besides being followed by a decrease in the fecal excretions of Ca and P, led to an increased urinary Ca excretion, no increase in the urinary P excretion, and an elevation of both Ca and inorganic P in the serum. Vit. D evidently increased the absorption of Ca, the other sequelae being secondary to this phenomenon. With the rising serum Ca level there occurred a decreased activity of the parathyroid glands (see below). 5. The fact that with the administration of vit. D the serum inorganic P value rose, whereas the urinary P excretion remained stationary or even fell, strongly suggested that the rise in the inorganic P level was due to an accompanying decreased activity of the parathyroid glands as a result of therapy (cf. decreased urinary P excretion and rising inorganic P level in serum with para-thyroidectomy). That the rise in serum inorganic P level was not due merely to increased absorption of phosphorus was shown by its failure to occur when phosphate was administered intraven. 6. In Patient 2 the intraven. administration of Ca was followed by no increase in the Ca excretion in the feces; the same amt. of Ca given by mouth caused a marked increase in the fecal Ca excretion. Since vit. D, thereafter, decreased the Ca excretion in the feces this was evidently due to increased absorption of Ca and not to decreased reexcretion into the gastro-intestinal tract. 7. In Patients 2, 3, and 4 with probably no functioning parathyroid tissue, vit. D therapy was followed by a falling serum inorganic P level. The rise in inorganic P which usually follows vit. D therapy is evidently the result of an accompanying decreased activity of the parathyroid glands. 8. In Patients 2, 3, and 4, the administration of large amts. of vit. D was followed by an increase in the urinary P excretion greater than, could be explained by the decreased fecal P excretion. Vit. D in addition to increasing the absorption of Ca probably increases the urinary excretion of P. Demineralization is probably due to this property of vit. D with large doses. 9A tentative diagram is presented for the relation to one another of the various sequelae following vit. D therapy. 10On the basis of the serum Ca and P values three types of vit. D deficiency are differentiated: (1) without parathyroid hyperplasia, (2) with compensatory hyperplasia, and (3) with hyperplasia, insufficient to cause compensation.