Primary Hyperparathyroidism—Evaluation of Diagnostic Aids: Calcium Infusion, Phosphorus Deprivation and Hydroxyprolinuria

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Abstract
The effect of an intravenous infusion of Ca on the urinary excretion of P and the effect of a P deficient diet plus Al gel on the urinary excretion of Ca were studied in the following groups of patients: a) surgically proven primary hyperparathyroidism, b) renal lithiasis, c) normal subjects. The average depression of urinary excretion of P in response to the intravenous infusion of Ca was: 32% for the normal subjects, [long dash]23% for the patients with renal lithiasis, and [long dash]7% for those with hyperparathyroidism. Although the average response in the group with hyperparathyroidism differs significantly from the response of the control subjects and the patients with renal lithiasis, the degree of individual overlap makes the clinical interpretation of this test hazardous. A similar conclusion was reached when the increments of the urinary excretion of Ca were observed during a period of P deprivation. Two out of 4 normal; 2 out of 6 stone-formers, and 6 out of 10 patients with hyperparathyroidism developed a calciuria about 250 mg/24 hr. Four patients with hyperparathyroidism failed to show any significant change during this maneuver. The 24-hr. urinary excretion of hydroxyproline on a low proteingelatin free diet was found to be elevated in 8 out of 17 patients with hyperparathyroidism. Only 3 of these 8 patients had elevated serum alkaline phosphatase levels. Hydroxprolinuria appears to be a more sensitive index of bone involvement than serum alkaline phosphatase in hyperparathyroidism, but the finding of a normal excretion of hydroxyproline does not exclude this diagnosis.