[Dysregulation of plasma 1,25(OH)2D in calcium restriction in hypercalciuric children].
BACKGROUND
The effect of calcium restriction on the plasma concentration of 1,25(OH)2D in normo- and hypercalciuric children remains unknown.


METHODS
We studied phosphate and calcium metabolism of 8 normocalciuric and 8 hypercalciuric children aged 4 to 16 years, under 3 conditions: on a normal dietary calcium intake after a 5-day calcium-restricted diet, and after oral calcium loading. The healthy, normocalciuric children had histories that included no renal failure of abnormalities of phosphate and calcium metabolism. Four of the 8 hypercalciuric children had urolithiasis, 1 had hematuria and the 3 others had idiopathic hypercalciuria. Blood samples were analyzed for calcium, creatinine, immunoreactive parathyroid hormone, cAMP, 25(OH)D and 1,25(OH)2D concentrations. Urine samples were analyzed for calcium, phosphorus, creatinine and cAMP.


RESULTS
On the normal dietary calcium intake, the hypercalciuric children had higher urinary calcium excretion and plasma 1,25(OH)2D levels and lower TmP that did the controls. The 1,25(OH)2D levels of the normocalciuric children were significantly increased after 5 days of dietary calcium deprivation, but those of the hypercalciuric children were not. The other parameters (essentially PTH, cAMP and TmP) varied similarly in the two groups.


CONCLUSIONS
The results suggest that: a) calcium restriction influences 1,25(OH)2D levels in normocalciuric subjects via a PTH- and phosphor-independent mechanism; b) dietary control of renal vitamin D metabolism is impaired in hypercalciuric patients.
Belon
C
C
Laboratoire de Biochimie I, Faculté de Pharmacie, Montpellier.
Dumas
R
R
Tau
C
C
Sabatier
R
R
Bourdeau
A
A
Garabedian
M
M
D000293:Adolescent; D002118:Calcium / Q000652:urine*; D002128:Calcium Metabolism Disorders / Q000097:blood / Q000188:drug therapy / Q000652:urine*; D002136:Calcium, Dietary / Q000494:pharmacology* / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D004100:Dihydroxycholecalciferols / Q000097:blood* / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male
D002136:Calcium, Dietary; D004100:Dihydroxycholecalciferols; D002118:Calcium
Dysrégulation du 1,25(OH)2D plasmatique au cours d'une restriction calcique chez des enfants hypercalciuriques.