A Rapid Calcium Infusion Test for Hyperparathyroidism

A rapid intravenous infusion of calcium (180 mg) was given to 10 normal subjects, to 7 patients with primary hyperparathyroidism (subsequently proved by surgery), to 1 patient with untreated hypoparathyroidism and to 13 patients with various other diseases. All studies were performed between 8 AM and 12 noon, during which interval spontaneous urinary phosphorus excretion normally shows a rise. Within 2 hours after the calcium infusion, phosphorus excretion by the normal subjects fell below that before the infusion, whereas phosphorus excretion by the patients with hyperparathyroidism was essentially unaffected. The patient with hypoparathyroidism, however, showed neither spontaneous nor postinfusion changes in phosphorus excretion. The patients with sarcoid showed a pattern of phosphorus excretion characterized by a rise, a fall and a further rise during successive hours after the infusion. All other patients showed a pattern indistinguishable from that of the normal subjects. The use of this rapid calcium infusion has enabled us to make the diagnosis of hyperparathyroidism in several patients who did not meet the usual laboratory criteria for this diagnosis.