Circadian rhythm with acrophase at night for urinary excretion of calcium and magnesium in childhood: population-based data of the cimitile study in southern Italy.

A population-based study on daily and overnight urine excretion of Ca and Mg was performed in 220 children aged 4-15 years living in Cimitile, Campania Region, Southern Italy. The Ca/creatinine and the Mg/creatinine ratio in overnight urine were significantly higher than in daily urine (p less than 0.01). This finding was also confirmed in hypercalciuric children. The Mg/Ca ratio in the general population was identical in daily and overnight urine while in the hypercalciuric group Mg/Ca in overnight urine was significantly higher (p less than 0.01) than in daily urine. The data point to the existence of a circadian rhythm with a peak at night for urine Ca and Mg excretion in children living in Cimitile and studied while attending to their everyday life.