ABSTRACT
In 22 of 28 cases of primary hyperparathyroidism (PHP) the rise in the serum immunoreactive parathyroid hormone (IRPTH or PTH) level observed in response to lowering of the serum calcium by EDTA, exceeded that obtained in 8 control subjects. In 5 of these 22 patients who were studied again after parathyroidectomy the supranormal response was abolished. Fifteen of these 22 hyper-responsive PHP patients had basal IRPTH levels not exceeding the highest level in the controls and that of other groups of patients investigated (idiopathic hypercalciuria, non-parathyroid hypercalcaemia, operated PHP). Fourteen of the 22 hyper-reactive patients with PHP did not show hypocalcaemia during the infusion of EDTA. The extent of the release of PTH elicited by EDTA in cases of PHP does not as yet allow a prediction of the amount of pathological parathyroid tissue present, although all the PHP patients showing a normal release of PTH had a relatively small mass of parathyroid tissue (up to about 1 g) subsequently removed. In 9 cases of nephrolithiasis (8 of whom had idiopathic hypercalciuria) and in 7 cases of non-parathyroid hypercalcaemia, a normal PTH release was found.
