Influence of Dietary Calcium on Serum 1,25‐dihydroxyvitamin D Concentrations in Renal Stone Formers

Abstract

The role of 1,25-dihydroxyvitamin D (1,25(OH)2D) in the pathogenesis of idiopathic hypercalciuria was studied in 37 renal stone formers who, during two 10-day periods, followed first a normal and then a low calcium diet. The following samples were taken during each diet; 24 h urine; fasting blood and urine; blood and urine following a 1 g oral calcium load. Patients were divided according to serum calcium level, 24 h urinary calcium excretion on the first diet and fasting calcium excretion on the second diet. Eight patients were found to be normocalciuric (NSF), 16 had absorptive hypercalciuria (AH), five renal hypercalciuria (RH) and eight primary hyperparathyroidism. In NSF and AH, a positive correlation was found between the fasting and the 24 hour urinary calcium (r = 0.787, P less than 0.001), while negative correlations were found between the fasting urinary calcium and the serum parathyroid hormone (r = -0.703, P less than 0.001) or the fasting urinary cyclic AMP (r = -0.434, P less than 0.01). Patients with RH had higher serum PTH and urinary cAMP levels for a given degree of fasting calciuria mainly on the low calcium diet. Mean serum 1,25(OH)2D was similar in NSF (43.6 +/- 4.5 pg/ml), AH (43.6 +/- 2.3 pg/ml) and RH (40.4 +/- 4.8 pg/ml) on the first diet; increases were similar in all groups after 10 d of calcium restriction. A positive correlation was found between the serum 1,25(OH)2D concentrations and the 24 h urinary calcium excretion on the first diet in NSF (r = 0.889, P less than 0.001) but not in AH or RH. There was no evidence of such correlation with the low calcium diet. No correlation between the calciuric response to calcium loading and the serum concentrations of 1,25(OH)2D was found. The results suggest that serum concentrations of 1,25(OH)2D may be related to urinary calcium excretion in NSF more than in AH or RH. The factors responsible for the hyperabsorption of calcium in the latter patients remain to be elucidated.

Association between Circulating Vitamin D Level and Urolithiasis: A Systematic Review and Meta-Analysis

“…After full-text analysis, another 19 studies were excluded for the following reasons: 14 had no control group and no useful data, three did not provide standard deviations, and two reported duplicate data. Finally, 32 studies fulfilled our eligibility criteria and were enrolled in the meta-analysis [10,11,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47]. …”

“…Most studies clearly demonstrated that they ruled out hyperparathyroidism and/or renal tubule acidosis [10,11,18,19,22,26,27,29,33,34,36,43], some also excluded patients using calcium and/or vitamin D [18,26,29,35,39,42]. Seventeen studies described their criteria of hypercalciuria and they were not consistent [18,19,20,22,24,26,28,29,32,35,36,37,38,42,43,45], twelve of which defined hypercalciuria as urinary calcium excretion of more than 300 mg/24 h for men and 250 mg for women or 4 mg/kg/day [19,23,26,28,29,32,35,36,38,42,43]. The subjects were on a free or normal calcium diet in some studies [10,11,19,21,22,26,28,29,32,35,36,39,43], while restricted calcium diets were adopted in some others [24,27,…”

“…Seventeen studies described their criteria of hypercalciuria and they were not consistent [18,19,20,22,24,26,28,29,32,35,36,37,38,42,43,45], twelve of which defined hypercalciuria as urinary calcium excretion of more than 300 mg/24 h for men and 250 mg for women or 4 mg/kg/day [19,23,26,28,29,32,35,36,38,42,43]. The subjects were on a free or normal calcium diet in some studies [10,11,19,21,22,26,28,29,32,35,36,39,43], while restricted calcium diets were adopted in some others [24,27,31,33,34,38]. Nineteen of the included trials only tested serum/plasma 1,25(OH) 2 D [19,20,22,24,26,27,28,30,31,32,33,34,35,36,37,38…”

“…The subjects were on a free or normal calcium diet in some studies [10,11,19,21,22,26,28,29,32,35,36,39,43], while restricted calcium diets were adopted in some others [24,27,31,33,34,38]. Nineteen of the included trials only tested serum/plasma 1,25(OH) 2 D [19,20,22,24,26,27,28,30,31,32,33,34,35,36,37,38,39,42,43], six only assessed 25(OH)D [18,25,40,41,44,47], and the others evaluated the two metabolites at the same time [10,11,21,22,29,45,46]. The most commonly used measurement method for 1,25(OH) 2 D and 25(OH)D was radioimmunoassay.…”

Osteocalcin, Parathormone and Hypercalciuria

“…In the SMA analysis, no changes were observed in calcemia, phosphoremia (which was never diminished), Cr, or total proteins, except in patients with resorptive hy percalciuria. [26]. All these contradictory findings exacerbate the controversy over the metabolic processes involved in the hypercalciurias, making establishment of uniform criteria for their study a priority.…”