Rapid Calcium Infusion Test for Hyperparathyroidism

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Abstract
The normal response to calcium infusion is a decreased urinary phosphate excretion, presumably as a result of inhibition of parathyroid hormone secretion by the induced hypercalcemia.1-3 In contrast, such a change in phosphaturia does not occur in the presence of hyperparathyroidism, and it has been suggested that the hyperfunctioning parathyroid tissue is absolutely or relatively autonomous, and hence unresponsive to changes in plasma calcium concentration.1 We have reported previously 4,5 the efficacy of a simple diagnostic test for hyperparathyroidism which takes advantage of this differential response to calcium infusion. Both normal subjects and patients with hyperparathyroidism exhibit a progressively increasing phosphaturia between the hours of 8 AM and 12 noon. The rapid infusion of calcium at 9 AM profoundly alters this phosphaturic rhythm in normal subjects, but has little or no effect upon the rhythm in patients with hyperparathyroidism. However, we have observed some limitations and potential sources