DKK1 (Dickkopf-1) is a secreted protein that functions as an inhibitor of the Wnt signaling pathway, which is key in regulating cell growth, development, and bone formation. By blocking Wnt interactions with its receptors, DKK1 influences processes such as cell differentiation, proliferation, and bone density. Its activity is linked to conditions like osteoporosis and several cancers, making it a potential target for therapeutic strategies.