Fibroblast growth factor 18 (FGF-18) is a growth factor and member of the FGF subfamily. FGF-18 is most similar to FGF-8 and FGF-17, and is secreted in adult lung and developing tissues (Ohbayashi et al.). FGF-18 signals through FGF receptor 3 (FGFR3) to regulate proliferation, differentiation, and matrix production of articular and growth plate chondrocytes in vivo and in vitro (Davidson et al.). FGF-18 has skeletal functions and protects articular cartilage by gene expression profiling and regulates proliferation and differentiation of midline cerebellar structures (Mori et al.). Also, recombinant human FGF-18 has been shown to effectively regulate hair growth (Song et al.).