It has been established for the first time that the gene RUNX2 in the promoter region is hypomethylated in postmenopausal women with osteoporosis at 1 CpG site, while in men over 50 years old with osteoporosis, all three studied CpG sites are hypomethylated, indicating the significant role of the aberrant DNA methylation of the RUNX2 gene in the development of this disease. The gene discussed is RUNX2; the disease is osteoporosis.