Moreover, gut dysbiosis and increased intestinal permeability reported in osteoporosis (He et al., 2020; Xu et al., 2020) induce activation of osteoclastogenic CD4+ T cells over-producing Rank-L and Tnf-α (D’Amelio et al., 2008; Li et al., 2016). The gene discussed is CD4; the disease is osteoporosis.