Sclerostin is a protein secreted by osteocytes that inhibits bone formation by osteoblasts. Deficiency of Sclerostin causes van Buchem disease and sclerosteosis, both rare sclerosing bone disorders, respectively. Interestingly, in humans, Sclerostin mRNA is expressed in several tissues, with high levels in the kidney whereas Sclerostin protein is only restricted to osteocytes. The exclusive effect of Sclerostin on bone formation and its deficiency causing bone disorders suggest a potential role of this molecule also in other diseases where bone homeostasis may be disarranged such as nephrolithiasis (16-18).