MAPK8 and osteoporosis: We systematically review literature on Wnt16 in senile, postmenopausal, and glucocorticoid-induced osteoporosis, focusing on its mechanisms of action: (1) regulating bone mineral density via genetic associations with GWAS-identified loci; (2) reducing cortical bone porosity and increasing thickness; (3) dual regulation of osteoblasts (via JNK/β-catenin pathways) and osteoclasts (via OPG-dependent/independent NF-κB pathways).