Calcium metabolism and blood pressure in children

Raised urinary calcium excretion has been reported in patients with essential hypertension, but it is not known whether this finding is an early expression of altered calcium metabolism or a consequence of longstanding high blood pressure (BP). BP and 24 h urinary excretion of calcium, sodium and creatinine were measured in a representative sample of healthy normotensive sixth grade school boys (n = 146: mean age 11.2 +/- 0.1 yrs, SEM). A significantly higher calcium output was found in children in the upper quarter of the BP distribution, even when differences due to body size, urinary creatinine and sodium excretion were excluded. The same result was obtained when students from the upper BP quartile were compared with age, height and weight-matched students from the rest of the study population (urinary calcium: 2.63 +/- 0.42 vs 1.54 +/- 0.23 mmol/24 h, P less than 0.02). Enhanced urinary calcium excretion is thus found in children in the upper part of the BP distribution for their age and sex and who are therefore at higher risk of hypertension in adulthood. This finding is compatible with the hypothesis of a primary abnormality of calcium metabolism in essential hypertension.