Loss of regulation of circulating 1,25-dihydroxyvitamin D with paradoxically decreased serum phosphate levels in individuals with recurrent kidney stones.

A low serum phosphate concentration is characteristic in individuals in whom kidney stones form, this being related to serum 1,25-dihydroxyvitamin D, parathyroid hormone and urinary phosphate excretion. In order to determine whether these parameters are related to recurrence of stone formation, they were analyzed in single and recurrent stone formers as well as controls. An inverse correlation between serum levels of phosphate and 1,25-dihydroxyvitamin D was observed in control subjects, indicating that a drop in serum phosphate results in upregulated circulating 1,25-dihydroxyvitamin D level in controls. While the circulating low phosphate level upregulated the 1,25-dihydroxyvitamin D level in single stone formers, the elevation was less than expected from the drop in serum phosphate in recurrent stone formers. The results thus suggest that loss of upregulation of 1,25-dihydroxyvitamin D by serum levels of phosphate might be important for stone formation. The possibility of deregulation of 1,25-dihydroxyvitamin D to maintain physiological requirements in stone formers and prevent further nephrolithiasis therefore warrants attention.