NORADRENERGIC BLOOD-PRESSURE DYSREGULATION AND CYTOSOLIC CALCIUM IN PRIMARY HYPERPARATHYROIDISM

The purpose of this study was to characterize the changes in noradrene rgic blood pressure regulation and the causes of this dysregulation in patients with histologically proven primary hyperparathyroidism befor e and after parathyroidectomy. In untreated hypertensive patients with primary hyperparathyroidism slightly higher plasma levels of norepine phrine, enhanced cardiovascular reactivity to norepinephrine (p<0.05) and increased cytosolic free calcium concentration in platelets (p<0.0 5) were found, Parathyroidectomy resulted in the correction of noradre nergic blood pressure dysregulation and in the reduction of cytosolic free calcium and led to normotension. In vitro incubation of platelets from normal subjects with heterologous plasma ultrafiltrates from eit her hypertensive patients with primary hyperparathyroidism or normoten sive uremic patients with secondary hyperparathyroidism led to raised platelet calcium in primary hyperparathyroidism but not in secondary h yperparathyroidism, although in both conditions intact parathormone le vels were elevated equally. Furthermore, when platelets of normotensiv e subjects were preincubated with commercially available parathormone, no effect on resting platelet cytosolic calcium was observed. Our res ults suggest that hypertension in primary hyperparathyroidism may be c aused in part by noradrenergic blood pressure dysregulation and seems to be causally linked to the secretion of a parathyroid hypertensive f actor, which increases cytosolic calcium and alters vascular tone and reactivity.