Dysregulation of medullary bone remodeling may contribute to development of osteoporosis in aged hens, which exhibit increased medullary bone expression of the resorption marker carbonic anhydrase 2 (CA2) and vitamin D3 receptor (VDR), as well as reduced expression of accretion proteins like collagen type 1 alpha 1 (COL1A1), relative to younger hens (Gloux et al., 2020b). This evidence concerns the gene CA2 and osteoporosis.