Some children with
Bartter syndrome have
hypercalciuria. To determine the mechanism for this phenomenon, we studied tubular function and
calcium metabolism in six such children. All patients had hypokalemic
alkalosis, normotension, hyperreninemia, growth retardation, low fractional distal
chloride reabsorption (4/5), and elevated urinary
prostaglandin E2 excretion (5/6). In addition, all had
hypercalciuria (urinary
calcium 6.5 to 25.0 mg/kg/day), with evidence of
nephrocalcinosis in five. None, however, had evidence of
rickets or
hyperparathyroidism. There was a marked elevation in the serum concentration of
1,25-dihydroxyvitamin D in all, and four patients had a response to oral
calcium loading suggestive of absorptive
hypercalciuria. Five children have had long-term
therapy with
indomethacin. They have had improvement in
hypokalemia and reduced urinary
prostaglandin E2 excretion as well as reductions in the serum concentration of
1,25-dihydroxyvitamin D and in urinary
calcium excretion. These data suggest that
hypercalciuria in some children with
Bartter syndrome is associated with an excess of
1,25-dihydroxyvitamin D. The improvement in
hypercalciuria with
prostaglandin synthesis inhibition may result in part from correction of this
vitamin D abnormality.