Antihypertensive effects of oral calcium supplementation may be mediated through the potent vasodilator CGRP.

Alteration of calcium metabolism and changes in the levels of calcium-regulating hormones have been described in essential hypertension. In the majority of the reported clinical trials, calcium supplementation has resulted in a decrease in blood pressure. However, the mechanisms by which such a response would be mediated are entirely unknown. The present study confirmed that daily supplementation with 1.4 g of elemental calcium led to a significant decrease in both systolic and diastolic blood pressures (P < .01). Decrease in blood pressure was negatively correlated with increase in plasma calcitonin gene-related peptide (CGRP), measured with radioimmunoassay and by radioreceptor assay (P < .001), and positively correlated with decrease in intact parathyroid hormone (PHT) (P < .05). Following cessation of calcium supplementation, plasma CGRP levels and the blood pressure both reverted back to the base-line values, suggesting a direct effect of supplemented calcium on these two parameters.