Strontium oral load test in children with idiopathic hypercalciuria

Increased intestinal calcium absorption may play an important role in the pathogenesis of idiopathic hypercalciuria in children. Calcium absorption was assessed by an oral strontium load test in 22 prepubertal children (13 male) with idiopathic hypercalciuria, urinary calcium excretion 6.48 +/- 0.60 mg/kg per day (range 4.12-13.40 mg/kg per day), and ten healthy, young, normocalciuric controls (six male). After administration of 2.65 mg/kg of strontium chloride (SrCl2), the serum concentrations of strontium at 30 min, 60 min, 120 min, 240 min, and the fraction of the absorbed dose (FAD%) at 30 min, 60 min and 240 min, were similar in both groups. FAD% at 120 min was lower (P < 0.05) in hypercalciuric children than in controls (11.84 +/- 0.96% vs 15.87 +/- 1.77%). Values of the area under the curve were not different between both groups. In children with idiopathic hypercalciuria, serum basal intact parathyroid hormone (PTH) (r=-0.59, P=0.004) and the 1,25-dihydroxyvitamin D/PTH ratio (r=0.65; P=0.001) were correlated with the serum concentration of strontium at 60 min. The study reported here provides, for the first time, the results of a strontium oral load test in children with idiopathic hypercalciuria. With this method no major alterations of intestinal calcium absorption were found in this disorder.