Key signals and pathways shared between osteoclasts and microglia, namely, myeloid cells 2 (TREM2) /DNAX Adaptor Protein 12 kD (TREM2/DAP12), macrophage colony-stimulating factor (M-CSF, also known as CSF1) and C-C-Motif Chemokine Receptor 5 (CCR5), converge through the Pyk2 pathway, which may be a common pathway for genetic correlation between osteoporosis and AD (Lee et al., 2021). The gene discussed is TREM2; the disease is Alzheimer disease.