TNFRSF11B and Osteopenia: The aim of our study was to determine the influence of the rs3102735 (−163A>G), rs3134070 (−245T>G), rs207361 (−950T>C), rs7844539 (6890A>C), and rs2073618 (1181G>C) polymorphisms of the OPG gene on the risk of osteoporosis and osteopenia in postmenopausal Polish women.