The Effect of Prednisone on Calcium Metabolism and Ca47 Kinetics in Patients with Multiple Myeloma and Hypercalcemia *

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Abstract
Five patients with multiple myeloma, four of whom were hypercalcemic, and two "normocalcemic" patients without bone disease or multiple myeloma were studied by combining metabolic balance and Ca47 kinetic studies to determine the effect of prednisone on calcium metabolism. Prednisone therapy resulted in a reduction in serum calcium concentration in all hypercalcemic patients but was without effect in the patients with normal serum calcium concentrations. In patients with multiple myeloma, prednisone therapy was associated with a decrease in the degree of negative balance or no change in calcium balance. Miscible calcium pool size, bone formation rate, and bone resorption rate as determined by Ca47 kinetic studies were elevated in the hypercalcemic myeloma patients and were reduced by prednisone therapy. Only small changes in calcium absorption and renal calcium transport were observed during prednisone therapy. No change in serum calcium binding during prednisone treatment was observed. It is, therefore, proposed that prednisone altered calcium exchange in and out of bone and favored the establishment of a new equilibrium at reduced pool size, in part through an antitumor effect on malignant plasma cells.