Relations between indices of mineral metabolism and blood pressure were examined in 182 subjects, comprising 58 patients with essential hypertension (EHT) and 124 healthy subjects attending a general health survey. Multivariate techniques of statistical analysis were employed to test the hypothesis of different relationships between blood pressure and calcium metabolism within the subpopulations and to eliminate confounding effects of age, sex and obesity.
Plasma ionized calcium was inversely related and the urinary calcium excretion positively related to blood pressure in the total group. This was not significantly different between the groups. Serum parathyroid hormone (PTH) was, however, related to diastolic blood pressure only in the EHT group. The EHT patients had significantly lower plasma levels of ionized calcium, significantly higher levels of PTH and significantly greater excretion of calcium in the urine than the healthy subjects.
The results of this investigation support the hypothesis that among patients with EHT the renal tubular reabsorption of calcium is impaired resulting in a reduction of plasma ionized calcium and thereby stimulation of PTH. The findings of linear relationships suggests the possibility of a direct association between calcium metabolism and the regulation of blood pressure.
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