TGFB1 and osteoporosis: In addition, another study identified single nucleotide polymorphisms (SNPs) in several TGF-β pathway components in patients with osteoporosis (TGFBR1, TGFBR2, Smad2, Smad3, Smad4, and Smad7) [203], but the relevance of these polymorphisms remains to be established.