Patients with essential hypertension, in particular those with low plasma renin activity (PRA), are reported to have lowered plasma-ionized calcium and elevated parathyroid hormone levels.

In this study 1 μg alphacalcidol (lα-hydroxy-vitamin D₃) was given in a double-blind, placebocontrolled fashion over four months to 39 subjects with mild to moderate hypertension. There was a significant rise in PRA in the treatment group when compared to placebo (P < .05), but the mean blood pressure response was similar in the two groups. When the treatment group was divided according to pretreatment PRA it was, however, seen that subjects with low PRA displayed a reduction in diastolic blood pressure, whereas those with high PRA raised their blood pressure compared to placebo. Also subjects with low pretreatment values for plasma-ionized calcium and high levels of parathyroid hormone showed a reduction in diastolic blood pressure. This study supports the idea of a relationship between calcium metabolism and the renin-aldosterone system in essential hypertension and describes a beneficial effect of vitamin D supplementation on blood pressure in low-renin hypertension. Am J Hypertens 1989;2:20-25