Association of Polymorphisms in Estrogen Receptor Genes ( ESR 1 and ESR 2) with Osteoporosis and Fracture—Involvement of Comorbidities and Epistasis

Single-nucleotide polymorphisms (SNPs) in the ESR 1/ ESR 2 genes play a role in osteoporosis (OP). Our objective was to determine associations of polymorphisms in ESR genes with OP and fracture, SNP–SNP interactions, and involvement of comorbidities. We analyzed 170 Mexican osteoporotic women (FNOP), 173 with hip fracture (HFx), and 210 controls. The SNPs, ESR 1 rs2234693CC, rs851982CC and rs1999805AA, were associated with reduced OP risk (odds ratios [ORs] = 0.35, 0.40 and 0.32, respectively; p < 0.05); rs2234693CC was associated with reduced fracture risk (OR = 0.24; p < 0.05). The obese/overweight carriers of rs9340799GG had a lower OP (OR = 0.15, p = 0.016) and fracture (OR = 0.12, p = 0.0057) risk. The rs9479055AA and rs3020404AA hypertensive carriers had a higher OP risk (OR = 5.96, p = 0.032; and OR = 5.29, p = 0.02, respectively). In addition, rs3020404AA had a higher risk of fracture (OR = 4.90, p = 0.045). The rs2228480GG hypertensive carriers had a higher risk of fracture (OR = 6.22, p = 0.0038). We found a synergic relation between the ESR 1 rs3020331 and rs1999805 in femoral neck OP and HFx. The rs2234693 ( Pvu II) and rs9340799 ( Xba I) polymorphisms are associated with a high risk forming a haplotype. The epistasis analysis suggests the contribution of both genes ( ESR 1/ ESR 2) to the risk of OP and fracture. Epistasis and involvement of obesity and hypertension lead to a significant modification of the risk.