Changes in calcium and magnesium metabolism in essential arterial hypertension

We studied 60 hypertensive patients (35 men and 25 women with an average age of 40 years) for signs of metabolic changes, with special emphasis on the relationship between the calcium and magnesium levels. The control group comprised 37 normotensive subjects (19 men and 18 women with an average age of 39 years). We studied the total serum calcium level (measured by atomic absorption), the ionized serum calcium level (by Nova 2 testing), and the plasma protein level, and we did coefficiency studies of the creatinine clearance and calcium and magnesium levels in 24-hour urine collections. In the hypertensive group, the ionized calcium level was significantly lower than that of the control subjects (P less than .001); the total serum calcium level was also lower, but the difference was of less statistical significance (P less than .05). There was no difference in serum magnesium levels between the two groups. There was a highly significant correlation between the total serum calcium level and the serum magnesium level (P less than .001) in the normal subjects; this correlation was not found in the hypertensive group. An increase in calcium and magnesium excretion was found in the 24-hour urine collections of the hypertensive group (P less than .001) (coefficient expressed as fractionated excretion of calcium and magnesium). There was also a high correlation between urinary excretion of calcium and magnesium (P less than .001) in the hypertensive subjects. Thus, the hypertensive subjects had changes in calcium metabolism that were related to magnesium levels. We suggest, therefore, that these two factors be studied simultaneously in evaluating patients with essential arterial hypertension.