Calcium and phosphorus homeostasis in man. Effect of corticosteroids

Serum calcium and phosphorus levels, urinary excretion rates of calcium, phosphorus, and cyclic adenosine monophosphate (cAMP), and plasma parathyroid hormone (PTH) concentrations were determined in 11 normal subjects and in nine patients maintained on long-term prednisone therapy for chronic obstructive pulmonary disease. These same determinations were repeated in five of the prednisone-treated patients during the course of a seven-day calcium infusion. Prior to the infusion, the prednisone-treated patients demonstrated significantly elevated serum levels of PTH (P less than .005) and increased rates of urinary phosphate and cAMP excreation (P less than .005) when compared with normal subjects. After initiation of calcium infusion, the previous elevations in all of these determinations decreased to near normal levels. These data suggest that the effects of secondary hyperparathyroidism in patients maintained on long-term prednisone therapy may be overcome when calcium is administered intravenously.