Relationship of volumetric bone mineral density and structural parameters with ER alpha gene polymorphisms

Bone mineral density (BMD) contributes to bone strength, and methods for clinical assessment of bone quality characteristics beyond what can be gathered by BMD are awaited. Peripheral quantitative computed tomography (pQCT) allows for separate assessments of cortical and trabecular bone, providing information on bone geometry. Previous studies examining the relationship between estrogen receptor alpha (ER alpha) gene polymorphisms and BMD have been performed in large populations. However, only limited information is available on the possible segregation of ER alpha gene polymorphisms with bone structural properties. The aim of our study was to evaluate the association of XbaI and PvuII ER alpha gene polymorphisms with QCT parameters. We studied 900 subjects (541 women, 449 men) participating to the InCHIANTI study. By tibial pQCT we evaluated trabecular volumetric BMD, cortical volumetric BMD, cortical bone area, and cortical thickness (CtTh). Subjects were genotyped for ER alpha gene PvuII and XbaI polymorphisms. Analysis of variance was used for statistical analysis. Male subjects with PP and XX genotypes had higher geometric parameters, and female subjects with XX and PP genotypes showed higher densitometric parameters than other genotypes; however, the differences did not reach statistical significance. After adjustment for potential confounders, we found a significant (P = 0.002) CtTh difference across PvuII polymorphism in male subjects, with higher CtTh values in PP genotypes with respect to Pp and pp genotypes. These results show a relationship between the presence of the P allele and higher values of CtTh in male subjects, indicating for ER alpha a role in the control of tibial bone geometry.