Families of children with idiopathic hypercalciuria. Evidence for the hormonal basis of familial hypercalciuria
L. C. Hymes and B. L. Warshaw
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.