DKK1 and osteoporosis: Inactivating mutations in LRP5 lead to osteoporosis-pseudoglyoma syndrome, characterized by severe early-onset osteoporosis and ocular malformation, whereas gain-of-function LRP5 mutations (which abolish interaction with inhibitors Dkk-1 and sclerostin) lead to the high bone mass syndrome endosteal hyperostosis (Worth disease) (11,36).