| Abstract: | Six children with idiopathic hypercalciuria and their families were examined with an oral calcium loading test. Family members were divided into two clinical categories: group 1 consisted of the six index children and their parents and siblings with urolithiasis or unexplained hematuria; group 2 comprised the remaining parents and siblings without signs or symptoms associated with hypercalciuria. The results revealed that fasting urinary excretion of calcium was similar in both groups, but group 1 displayed a greater calciuric response to an oral calcium load. Serum concentrations of calcitriol (1,25-dihydroxyvitamin D3) and calcium were higher in group 1 than in group 2, while parathyroid activity was lower in group 1 patients. Urinary excretion of sodium, phosphorus, and magnesium, urine pH, serum levels of calcifediol (25-hydroxyvitamin D3) and phosphorus, and the renal tubular threshold for phosphate were not significantly different in the two groups. These findings suggest that idiopathic hypercalciuria may arise from a disturbance in the regulation of vitamin D metabolism that mediates enhanced intestinal absorption of calcium. |
