Background: Secondary hyperparathyroidism is a frequent metabolic complication of bariatric surgery. Individual differences in calcium absorption determine chronic secondary hyperparathyroidism after biliopancreatic diversion in half of the patients who have normal levels of 25-hydroxyvitamin D. We aimed to evaluate if certain vitamin D receptor polymorphisms may be responsible for the latter. Cases and controls study including 57 patients after biliopancreatic diversion with a mean serum 25-hydroxyvitamin D above 20 ng/mL, separated into those with secondary hyperparathyroidism (n = 26, cases) and those without it (n = 31, controls).
Methods: Genotyping for restriction-length-fragment polymorphisms of the vitamin D receptor gene was carried out for FOK1, BSM1, APA1, and TAQ1, and haplotype structure was also constructed.
Results: There were no differences in the allelic or genotypes distribution of the four studied polymorphisms between patients and controls (P = 0.352 and P = 0.301 for FOK1, P = 0.733 and P = 0.924 for BSM1, P = 0.974 and P = 0.992 for APA1, and P = 0.995 and P = 0.928 for TAQ1, respectively). Haplotype analysis showed no differences between patients and controls (P = 0.495 for BAT, P = 1.000 for BAt, P = 0.508 for Bat and P = 0.924 for bAT haplotypes, respectively). Furthermore, haplotypes were not associated with serum PTH levels or with the ratio between serum PTH and 25-hydroxyvitamin D levels.
Conclusion: Chronic secondary hyperparathyroidism after biliopancreatic diversion in patients with normal levels of 25-hydroxyvitamin D is not dependent on vitamin D receptor gene polymorphisms.