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Research Article Free access | 10.1172/JCI107498
Medical and Research Services, Veterans Administration Wadsworth Hospital Center, Los Angeles 90073
Department of Medicine, Cedars Sinai Medical Center, Los Angeles, California 90024
Department of Medicine, University of California Los Angeles School of Medicine, Los Angeles, California 90024
Section of Orthopedic Research, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901
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Medical and Research Services, Veterans Administration Wadsworth Hospital Center, Los Angeles 90073
Department of Medicine, Cedars Sinai Medical Center, Los Angeles, California 90024
Department of Medicine, University of California Los Angeles School of Medicine, Los Angeles, California 90024
Section of Orthopedic Research, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901
Find articles by Coburn, J. in: JCI | PubMed | Google Scholar
Medical and Research Services, Veterans Administration Wadsworth Hospital Center, Los Angeles 90073
Department of Medicine, Cedars Sinai Medical Center, Los Angeles, California 90024
Department of Medicine, University of California Los Angeles School of Medicine, Los Angeles, California 90024
Section of Orthopedic Research, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901
Find articles by Hartenbower, D. in: JCI | PubMed | Google Scholar
Medical and Research Services, Veterans Administration Wadsworth Hospital Center, Los Angeles 90073
Department of Medicine, Cedars Sinai Medical Center, Los Angeles, California 90024
Department of Medicine, University of California Los Angeles School of Medicine, Los Angeles, California 90024
Section of Orthopedic Research, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901
Find articles by Friedler, R. in: JCI | PubMed | Google Scholar
Medical and Research Services, Veterans Administration Wadsworth Hospital Center, Los Angeles 90073
Department of Medicine, Cedars Sinai Medical Center, Los Angeles, California 90024
Department of Medicine, University of California Los Angeles School of Medicine, Los Angeles, California 90024
Section of Orthopedic Research, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901
Find articles by Brickman, A. in: JCI | PubMed | Google Scholar
Medical and Research Services, Veterans Administration Wadsworth Hospital Center, Los Angeles 90073
Department of Medicine, Cedars Sinai Medical Center, Los Angeles, California 90024
Department of Medicine, University of California Los Angeles School of Medicine, Los Angeles, California 90024
Section of Orthopedic Research, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901
Find articles by Massry, S. in: JCI | PubMed | Google Scholar
Medical and Research Services, Veterans Administration Wadsworth Hospital Center, Los Angeles 90073
Department of Medicine, Cedars Sinai Medical Center, Los Angeles, California 90024
Department of Medicine, University of California Los Angeles School of Medicine, Los Angeles, California 90024
Section of Orthopedic Research, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901
Find articles by Jowsey, J. in: JCI | PubMed | Google Scholar
Published December 1, 1973 - More info
Studies were carried out to evaluate the mechanism of hypocalcemia in magnesium depletion. Day old chicks fed a magnesium deficient diet developed marked hypocalcemia, with a direct relation between serum calcium (y) and magnesium (x): y = 2.68 x + 4.24, r = 0.84 (both in mg/100 ml). Injections of parathyroid extract that increased serum calcium 2-3 mg/100 ml in normals had no effect in Mg-depleted birds. Very large dietary supplements of calcium or vitamin D3 increased mean serum calcium only from 5.3 to 7.7 and 7.8 mg/100 ml, respectively, while a normal magnesium diet for 3 days increased calcium from 5.3 to 9.9 mg/100 ml despite absence of dietary calcium. Intestinal calcium transport, studied in vitro, and the calcium concentration of the carcass was significantly increased in magnesium-depleted chicks, making it unlikely that reduced intestinal absorption of calcium caused the hypocalcemia. In magnesium-deficient chicks, the bone content of magnesium was decreased by 74%, the calcium content was unchanged, and the cortical thickness of bone was markedly increased. After 3 days of magnesium-repletion, cortical thickness was reduced with increased endosteal resorption. There was an increase in unmineralized osteoid tissue in the magnesium-depleted chicks. Parathyroid gland size and histology did not differ in magnesium-depleted and control birds. The results suggest that hypocalcemia develops due to altered equilibrium of calcium between extracellular fluid and bone, favoring increased net movement into the latter. Failure of parathyroid gland function could also exist, and unresponsiveness to parathyroid hormone (PTH) may also contribute to the hypocalcemia. However, failure of PTH action is probably due to the presence of excess osteoid tissue rather than a primary event leading to hypocalcemia.
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