Idiopathic hypercalciuria ( IH ) is an important risk factor for calcium oxalate nephrolithiasis. there appear to be two types: absortive hypercalciuria ( AH ), in which there is increased calcium ( Ca ) absorption from the gut, and renal hypercalciuria, in which the primary abnormality is decreased renal tubular Ca reabsorption. One of the potential mechanisms for the basic abnormality in AH is the primary increase in enterocyte Ca transport resulting in an increase in the serum Ca level and the renal filter load.
1,25-Dihydroxyvitamin D3 ( 1,25 ( OH )2D3 ) play a key role in the intestinal absorption of Ca and raises the serum Ca concentration. 1,25 ( OH ) 2D3 exerts its activity by binding the vitamin D receptor. The pathogenetic significance of 1,25 ( OH ) 2D3 in AH is not clearly defined. li et al. suggested that the increased Ca absorption is mediated by an increase in the number of intential VDR in genetic hypercalciuric rats. Zarwekh et al. reported increased VDR number in activited lymphocytes from some patients with AH who had normal 1,25 ( OH ) 2D3 levels.
The VDR gene consist of nine exon and has several polymorphism in intron 8 and exon 9. Recently, relationships between VDR gene polymorphism and Ca homeostasis have been addressed in some studies. Allelic variation in the VDR gene has been suggested as a partial explanation of diferential Ca absorption in premenopausal women. furthermore, the association of VDR gene polymorphism with Ca stones has been detected in several studies. since increased Ca absorption from the gut is believed to be involved in the pathogenesis of IH can be expected. The aim of this study was to investigate the association between VDR gene polymorphism and AH
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