Understanding of the molecular mechanisms involved in promoting bone density has been important to the development of multiple drug therapies for osteoporosis, such as the capthepsin K inhibitors Odanacatib (Eisman et al., 2011) and Balicatib (Adami et al., 2006), anti-SOST antibodies (Padhi et al., 2011), anti-Dkk1 antibodies (Hoeppner et al., 2009), and GSK3β and Sfrp1 inhibitors (Kulkarni et al., 2006; Moore et al., 2009). Here, SFRP1 is linked to osteoporosis.