It is well known that loss of function or gain of function mutations in the Lrp5 gene lead respectively to a low or high bone mass phenotype, as clinically observed in Osteoporosis Pseudoglioma Syndrome (OPPG) and the High-bone-mass Syndrome (HBM)[42,43] and the majority of researchers interpret this as the result of Wnt signaling inhibition in osteoblasts. Here, LRP5 is linked to osteoporosis-pseudoglioma syndrome.