Normal vitamin D and mineral metabolism in essential hypertension

The effects of dietary sodium upon serum and urinary calcium and selected vitamin D metabolites were studied in two groups (n = 10 each) of age and gender matched, white normotensive subjects and patients with normal-renin hypertension. Isocaloric diets were consumed on a metabolic ward with sequential daily sodium intake of 109 meq for 5 days and 9 meq and 259 meq for 6 days each. Values for serum and urinary calcium, phosphorus, magnesium and electrolytes, creatinine clearance, plasma immunoreactive parathyroid hormone, and serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were similar in both study groups on each diet. Measurements of plasma renin activity and serum aldosterone levels were higher in the hypertensive than in the normotensive group on each diet (p less than .05-.01). Serum 1,25-dihydroxyvitamin D and urinary calcium increased on the high sodium diet in the normotensive (p less than .05) and the hypertensive groups (p less than .01). When the data for normotensive subjects and hypertensive patients were pooled by gender, males had a 1 1/2 to 3 times the urinary calcium excretion than females, regardless of diet. The present study indicates that there are no differences in the selected components of calcium and vitamin D metabolism in response to sodium intake in patients with essential hypertension and normal plasma renin activity as compared to normal controls.