Urinary excretion of calcium and magnesium in children

Abstract

Urine calcium excretion in healthy children was 2·38±0·66 (SD; no. = 52) mg/kg per 24 hr and urinary magnesium excretion was 2·82±0·79 (SD; no. = 23). The 24-hour urine calcium excretion could be predicted with reasonable confidence from the calcium/creatinine concentration ratio of the second urine specimen passed in the morning. In this specimen the urine calcium/creatinine concentration ratio was 0·14±0·06 (SD; no. = 60) mg/mg and the magnesium/creatinine concentration ratio was 0·21±0·10 (SD; no. = 29) mg/mg.

The upper limit of the urine calcium excretion is taken to be 4 mg/kg per 24 hr and that of the calcium/creatinine concentration ratio in the second morning urine is 0·25 mg/mg. After a milk load of 700 ml/1·73 m² the urinary calcium/creatinine concentration ratio rose in the first two hours, but in no sample exceeded 0·25 mg/mg.