Sclerostin is a secreted glycoprotein with a C-terminal cysteine knot-like (CTCK) domain and sequence similarity to the DAN (differential screening-selected gene aberrative in neuroblastoma) family of bone morphogenetic protein (BMP) antagonists. Loss-of-function mutations in this gene are associated with an autosomal-recessive disorder, sclerosteosis, which causes progressive bone overgrowth. A deletion downstream of this gene, which causes reduced sclerostin expression, is associated with a milder form of the disorder called van Buchem disease.Sclerostin is produced by the osteocyte. These cells originate from osteoblasts, the cells that form the bone matrix. Sclerostin has an inhibitory effect on the life time of the osteoblast. Osteoblasts are self limiting by a negative feedback system.