DKK-1 protein is a secreted protein belonging to the DKK protein family that plays crucial roles in various biological processes. DKK-1 serves as an effective antagonist of canonical Wnt signaling, inhibiting the interaction between LRP5/6 and Wnt. It forms a ternary complex with KREMEN, leading to the internalization of LRP5/6. Additionally, DKK-1 has pro-apoptotic functions independent of Wnt antagonism through KREMEN1 and exhibits anti-apoptotic activities. This protein is associated with limb development, ensuring normal limb patterning by regulating Wnt signaling. DKK-1 protein has potential applications in diagnostic testing for osteoporosis, bone tumors, bone metabolic diseases, and cardiovascular disease risk assessment. For instance, measuring DKK-1 levels in serum or urine can aid in the diagnosis and assessment of osteoporosis severity and fracture risk. In bone tumor diagnosis, elevated DKK-1 expression may provide auxiliary evidence and be used for prognostic evaluation. Additionally, DKK-1 is associated with various bone metabolic diseases such as rheumatoid arthritis and hyperparathyroidism, where it serves as an important biomarker for diagnosis and monitoring.