CYP2R1 and asthma: Our study was carried out in order to ascertain the influence of eight genetic polymorphisms located in the main genes that regulate vitamin D metabolism (CYP24A1, GC, CYP27B1 and CYP2R1) and five SNPs in the gene that encodes its receptor (VDR) on the susceptibility to asthma, in a Caucasian population in southern Spain.