TNF and osteoporosis: Moreover, the allelic variants of the TNF-α gene and BMD, including those between SNPs rs1800630 (-863C/A) and rs1800630 (-1031T/C) of the TNF-α gene and low BMD [16, 17] are associated to a dinucleotide repeat polymorphism in TNF-α for linkage to osteoporosis [21].