Increased Serum 1,25-(OH)2-Vitamin D Concentrations Fail to Affect Serum or Urine Phosphate in Humans
Patients with recurrent calcium oxalate/apatite nephrolithiasis in association with hypercalciuria (idiopathic hypercalciuria) may exhibit low serum inorganic phosphate concentrations (1,2,3,4) in association with normal rates of urinary phosphate excretion implying the existence of impaired renal tubular phosphate reabsorption. In fact, such calcium stone formers exhibit impaired renal phosphate conservation in response to ingestion of a diet low in phosphate (5). They also exhibit higher than normal salivary phosphate concentrations (6) implying the presence of a more generalized abnormality of phosphate transport. Dietary phosphate deprivation in animals is accompanied by increased synthesis of the calcium mobilizing steroid 1,25-(OH)2-vitamin D3 by the kidney (7) and elevated serum levels of this hormone (8). Similarly renal synthesis of 1,25-(OH)2-D is increased in hypercalciuric kidney stone formers (9) and high serum 1,25-(OH)2-D concentrations among these patients may be inversely related to the degree of hypophosphatemia (4).
KeywordsPhosphorus Magnesium Creatinine Hyperparathyroidism Nephrolithiasis
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- 3.Shen, F.H., Baylink, D.J., Neilsen, R.L., Sherrard, D.J., Ivey, J.L. and Haussler, M.R. Further evidence supporting the phosphate leak hypothesis of idiopathic hypercalciuria. Proceedings of the Third International Workshop on Phosphate and other Minerals, Madrid, July, 1977. In Homeostasis of Phosphate and Other Minerals, S.G. Massry, E. Ritz and A. Rapado, Editors. Plenum Press, New York, 1978, 217.Google Scholar
- 4.Gray, R.W., Wilz, D.R., Caldas, A.E., and Lemann, J. Jr. 1977 The importance of phosphate in regulating plasma 1,25-(OH)2-vitamin D levels in humans: Studies in healthy subjects, in calcium-stone formers and in patients with primary hyperparathyroidism. J. Clin. Endocrinol. Metab. 45: 299.PubMedCrossRefGoogle Scholar
- 5.Lemann, J. Jr., Gray, R.W., and Wilz, D.R. 1978. Evidence for a renal PO4 leak in patients with calcium nephrolithiasis. Proceedings of the Third International Workshop on Phosphate and other minerals, Madrid, July, 1988. In Homeostasis of Phosphate and Other Minerals, S.G. Massry, E. Ritz and A. Rapado, Editors. Plenum Press, New York, 225.Google Scholar
- 6.Lemann, J. Jr., Gray, R.W., Wilz, D.R. and Adams, N.D. 1979. Is there a disorder of phosphate metabolism in idiopathic hypercalciuria? Proceedings of the 4th Workshop on Phosphate, Strasbourg, June, 197 9. In Phosphate and Minerals in Health and Disease, S.G. Massry, E. Ritz, and H. Jahn, Editors. Plenum Press, New York, 1980, 427.Google Scholar
- 7.Gray, R.W., 1981. Dietary phosphate deprivation increases 1,25-(OH)2-vitamin D3 synthesis in rat kidney. Federation Proceedings: 40: 899.Google Scholar
- 12.Brickman, A.S., Hartenbower, D.L., Norman, A.W. and Coburn, J.W. 1977. Actions of 1α-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 on mineral metabolism in man. J. Clin. Nutr. 30: 1064.Google Scholar
- 13.Perlik, M. and Wasserman, R.H. 1978. Effect of vitamin D on transepithelial phosphate transport in chick intestine. Am. J. Physiol. 234: E399.Google Scholar