DKK1 (Dickkopf-1) is a secreted protein that acts as an inhibitor of the Wnt signalling pathway, which plays a crucial role in regulating cell growth, development, and bone formation. By preventing Wnt from binding to its receptors, DKK1 affects processes such as cell differentiation, proliferation, and bone density. Its function is associated with conditions like osteoporosis and various cancers, making it a potential target for therapeutic approaches.