Noradrenergic blood pressure dysregulation and cytosolic calcium in primary hyperparathyroidism

The purpose of this study was to characterize the changes in noradrenergic blood pressure regulation and the causes of this dysregulation in patients with histologically proven primary hyperparathyroidism before and after parathyroidectomy. In untreated hypertensive patients with primary hyperparathyroidism slightly higher plasma levels of norepinephrine, enhanced cardiovascular reactivity to norepinephrine (p<0.05) and increased cytosolic free calcium concentration in platelets (p<0.05) were found. Parathyroidectomy resulted in the correction of noradrenergic 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 either hypertensive patients with primary hyperparathyroidism or normotensive uremic patients with secondary hyperparathyroidism led to raised platelet calcium in primary hyperparathyroidism but not in secondary hyperparathyroidism, although in both conditions intact parathormone levels were elevated equally. Furthermore, when platelets of normotensive subjects were preincubated with commercially available parathormone, no effect on resting platelet cytosolic calcium was observed. Our results suggest that hypertension in primary hyperparathyroidism may be caused in part by noradrenergic blood pressure dysregulation and seems to be causally linked to the secretion of a parathyroid hypertensive factor, which increases cytosolic calcium and alters vascular tone and reactivity.