ESRRA and osteoporosis: Bonnelye et al. demonstrated that the down-regulation of ERRα expression by antisense treatment of rat calvaria cells not only inhibits osteogenesis but also increases adipocyte colony formation and changes the OPG/receptor activator of the nuclear factor kappaB ligand ratio; these findings indicate that ERRα may play a functional role in osteoblasts, adipocytes, osteoclasts, etc. in E2 deficiency diseases, such as osteoporosis, which is regulated by estrogen in bone [9].