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The effects of pharmacological doses of dexamethasone on calcium metabolism were evaluated in 4 normal subjects, by stable calcium and phosphorus balances and 47Ca kinetic studies. The radioactivity data were satisfactorily fitted to a model with 2 exchanging compartments.There was a significant increase in urinary calcium excretion rate with higher specific activities. The total faecal calcium did not alter despite changes in its components, i. e. a fall in endogenous faecal calcium and an increase in unabsorbed dietary calcium. The data suggest that dexamethasone inhibits the rate of calcium transfer across the intestinal wall. more intensely from the mucosal cell to the lumen (secretion).From the constants of compartmental analysis, the only significant and consistent change was the increase in bone resorption rate. Bone deposition rate increased in 2 and decreased in the remaining 2 subjects.The results of our studies indicate that dexamethasone has a direct effect on the way calcium is dealt with by the kidney and the gut and that the drug has a direct effect on the skeleton.For comparison a patient with Cushing's syndrome was studied during the active phase and also after clinical and laboratorial remission of the disease.