SOST and Norrie disease: The bone formation inhibitor sclerostin encoded by SOST binds in vitro to low density LRP5/6 (lipoprotein receptor-related protein) Wnt coreceptors, thereby inhibiting Wnt/β-catenin signaling, a central pathway of skeletal homeostasis, and LRP5 deficiency results in OPPG (osteoporosis-pseudoglioma), whereas SOST deficiency induces lifelong bone gain in mice and humans [7].