Association between vitamin D receptor gene polymorphism and relative hypoparathyroidism in patients with chronic...

To study the influence of vitamin D receptor (VDR) gene polymorphism on parathyroid cell function in chronic renal failure, 85 patients who had serum PTH levels <12 pmol/L (the low intact PTH [iPTH] group) and 46 patients who had serum iPTH levels >60 pmol/L (the high iPTH group) were selected out of a total dialysis population of 170 individuals. As a result of subsequent exclusions based on several criteria in both groups (diabetic patients, serum aluminum levels, serum calcium levels, and time on dialysis), the final low iPTH group consisted of 34 patients and the final high iPTH included 32 patients. A healthy control population (n = 120) and 162 of the 170-patient dialysis population served as control groups. VDR gene polymorphism was determined by digestion with the BsmI enzyme and single-strand conformation polymorphism analysis of PCR amplified fragments. Serum iPTH levels were lower in patients with the BB genotype than in those with the Bb or bb genotype, both in the total dialysis population and when the various exclusion criteria were applied. No differences in genotypic and allelic frequencies were found between the healthy control population and the high iPTH group. However, the genotypic distribution was significantly different in the low iPTH group of patients before and after applying all exclusion criteria (P = 0.037 and P = 0.018, respectively). In the final selected population, the bb genotype was less frequent in the low iPTH group than in the total dialysis population (14.7% versus 36.4%; odds ratio, 0.3; confidence interval, 0.11 to 0.82; P = 0.01). Conversely, the BB genotype was over-represented in the low iPTH group (23.3% versus 19.7%; odds ratio, 1.9; confidence interval, 0.85 to 4.3; P = 0.1). In addition, the bb genotype and the b allele frequencies were lower in the low iPTH group than in the high iPTH group (14.7% versus 34.4%, P = 0.06, and 41.2% versus 60.9%, P = 0.02, respectively), and the BB genotype and the B allele were significantly more frequent in the low PTH group than in the high iPTH group (32.3% versus 12.5%, P = 0.05, and 58.8% versus 39.1%, P = 0.02, respectively). Thus, VDR gene polymorphism influences parathyroid function in chronic renal failure.