Serum calcium fractions in essential hypertensive and matched normotensive subjects.

Concentrations of serum total calcium and serum calcium fractions were compared between 28 hypertensive subjects and 28 race-sex-age-matched normotensive controls. Mean levels of serum total calcium were not different between the two groups. Hypertensive subjects had lower mean serum levels of ultrafilterable calcium (-0.32 mg/dl; p = 0.01), ionized calcium (-0.07 mg/dl; p = 0.09), and complexed calcium (-0.23 mg/dl; p = 0.04) and higher levels of protein-bound calcium (+0.36 mg/dl; p = 0.07). Estimated dietary calcium intake was similar in the two groups. These findings add to the evidence that essential hypertension is associated with perturbations in calcium metabolism.