Sex-dependent relation between ionized calcium in serum and blood pressure.

In an epidemiological study of 977 45-year-olds, both the mean concentration of ionized calcium in serum, [Ca2+]7.4, and arterial blood pressure were higher in men than in women. Among the men, there was a weak positive correlation between [Ca2+]7.4 and the systolic blood pressure, but no other significant correlation was found within each separate sex. Postmenopausal women had slightly increased [Ca2+]7.4 but normal blood pressure. Patients taking thiazide diuretics or beta-adrenergic blocking agents had normal [Ca2+]7.4.