Insulinlike growth factor binding protein7, also known as mac25, a 256 aa secreted protein and member of a growing family of IGFBPs which regulate the biological activities and distribution of the insulinlike growth factors (IGFs), through binding to IGFI and IGFII. IGFBP7 is widely expressed throughout normal tissues, but is also expressed in many tumor types at an increased or reduced level, and acts as a suppressor of breast and prostate cancer cell lines. IGFBP7 inhibits IGFinduced differentiation of skeletal muscle (myogenesis) and has implications in bone formation, by its possible affects on the actions of parathyroid hormone (PTH) and cortisol.