Calcium, parathyroid hormone, and blood pressure.

This review critically analyzes the available information on the relationship among calcium, parathyroid hormone, and blood pressure regulation. Both acute and chronic hypercalcemia increase blood pressure primarily via direct effects on vascular smooth muscle contractility. The evidence for indirect effects through activation of hormonal pressor systems is inconclusive. In apparent contrast with the notion that hypercalcemia can cause hypertension, more recently it has been proposed that calcium deficiency may be important in the genesis of hypertension both in humans and in spontaneously hypertensive animals. However, the evidence supporting this notion is still conflicting. Parathyroid hormone exerts complex actions on the cardiovascular system. On one hand, if injected in pharmacological doses, it is a vasodilator and antagonizes the pressor action of norepinephrine and angiotensin II; on the other hand, parathyroid hormone can potentiate the pressor effect of hypercalcemia.