Calcium metabolism in essential hypertension: relationship to altered renin system activity.

Hypertensive disease is associated with various abnormalities of calcium metabolism although how these abnormalities relate to the elevated pressure remains unclear. Based on the use of renin-sodium profiling, we have defined heterogeneous deviations in circulating levels of ionized calcium and magnesium as well as of the calcium-regulating hormones parathyroid hormone, calcitonin, and 1,25-dihydroxyvitamin D (1,25D), which parallel similar deviations in plasma renin activity. Essential hypertensive subjects with a profile of low renin, lower ionized calcium, and elevated 1,25D respond best to the calcium channel blocker nifedipine, demonstrate an enhanced sensitivity to the blood pressure effects of dietary salt loading, and have significantly lower blood pressures in response to oral calcium supplementation. Hypertensive subjects with the opposite metabolic profile--higher renin activity, higher serum ionized calcium, and lower 1,25D levels--are relatively insensitive to the blood pressure effects of either dietary salt loading or nifedipine, and show no significant hypotensive response to calcium supplements. Altogether, these alterations of calcium ionic and hormonal metabolism suggest that the hormonal control of calcium metabolism is linked to renin system activity as well as to the pathophysiology of the hypertensive process.