[Metabolic effects of Cholecalciferol supplementation in kidney stone formers with vitamin D deficiency].

INTRODUCTION: In this paper we investigated whether cholecalciferol supplementation, prescribed to treat vitamin D deficiency in patients with nephrolithiasis, increased the risk of stone recurrence.

METHODS: Calcium excretion and urine supersaturation with calcium oxalate (βCaOx) and brushite (βbsh) were evaluated in 33 kidney stone formers (aged 56±17; 12 males), both before and after therapy with cholecalciferol, prescribed as oral bolus of 100.000-200.000 UI, followed by maintenance doses, repeated every week (5.000-10.000 UI) or month (25.000-50.000 UI). During the study, patients followed a dietary regimen which included a daily calcium intake of about 800-1000 mg.

RESULTS: Urinary nitrogen, sodium and ash-acid excretion did not significantly change during the study. After cholecalciferol supplementation, the main results were as follows: both serum calcium and phosphate did not vary significantly; 25(OH)VitD₃ increased from 11,8±5,5 to 40,2±12,2 ng/mL (p<0,01); 1,25(OH) ₂ VitD₃ increased from 41,6±17,6 to 54,0±16,0 pg/mL (p<0,01); PTH decreased from 75,0±27,2 to 56,7±21,1 pg/mL (p<0,01); daily urinary calcium increased from 2,7±1,5 to 3,6±1,6 mg/Kg b.w. (p<0,01), whereas fasting urinary calcium did not change significantly. After therapy, βbsh increased from 0,9±0,7 to 1,3±1,3 (p=0,02) and βCaOx did not vary significantly. Before cholecalciferol supplementation, 6/33 patients (18.2%) were hypercalciuric, whereas 13/33 patients (39,4%) showed hypercalciuria after supplementation (pX²=0,03).

CONCLUSIONS: Cholecalciferol supplementation for vitamin D deficiency may increase both urinary calcium and urine supersaturation in stone formers. If vitamin D supplements are needed in these patients, a careful monitoring of urine metabolic profile is warranted, in order to customize the metaphylaxis accordingly (hydration, potassium citrate, thiazides).