Bone metabolism is a term describing the constant production and degradation of bone tissue, necessary for its maintenance and repair. The production and degradation of bone are the result of the activity of osteoblasts and osteoclasts, respectively. A disturbance of this balance can lead to excessive bone degradation (osteoporosis), but also to an increased bone density (sclerosing bone disorders). Several mutations in components of WNT signaling have been associated with aberrant bone metabolism, as will be discussed below.