Insulin-like growth factor-binding protein 3 (IGFBP-3), in humans, is encoded by the IGFBP3 gene.IGFBP-3 is one of six IGF-binding proteins (IGFBP-1 to 6) that have a highly conserved structure and bind with high affinity to IGF-1 and IGF-2.IGFBP-3 is the major transporter protein of IGF in the blood. It interacts with cell surface proteins to influence extracellular or post-internalized cellular signals, and it can also enter the nucleus where it binds nuclear hormone receptors and other ligands. Based on cell growth experiments, animal cancer models and epidemiological studies, IGFBP-3 appears to act as a tumor suppressor gene with low epistasis. Dysregulated IGFBP-3 is involved in many cancers. Serum levels of IGFBP-3 can be used to screen for growth hormone deficiency. IGFBP-3 levels are decreased in the serum of patients with AIDS, uncontrolled diabetes, trauma and severe burns.