Sclerostin is a recently identified glycoprotein expressed and synthesized by osteocytes. It is a powerful inhibitor of osteoblasts proliferation and differentiation. Sclerostin inhibits the Wnt signaling, the main trigger of osteoblasts activity. Osteocytes on response to a mechanical loading decrease the synthesis of sclerostin enabling in osteoblasts the Wnt signaling and promote their bone-forming activity. This explains why mechanical loading induces bone formation. Monoclonal antibodies directed against sclerostin reverses sclerostin induced bone catabolic effect and are promising tool in prevention and treatment of osteoporosis in human.