This gene is a member of the insulin-like growth factor binding protein (IGFBP) family and encodes a protein with an IGFBP domain and a thyroglobulin type-I domain. The protein binds both insulin-like growth factors (IGFs) I and II and circulates in the plasma. Binding of this protein prolongs the half-life of the IGFs and alters their interaction with cell surface receptors. [provided by RefSeq, Jul 2008], function: IGF-binding proteins prolong the half-life of the IGFs and have been shown to either inhibit or stimulate the growth promoting effects of the IGFs on cell culture. They alter the interaction of IGFs with their cell surface receptors. Promotes cell migration., PTM: Phosphorylated; probably by casein kinase II. Alters the affinity of the protein for IGFs., similarity: Contains 1 IGFBP N-terminal domain., similarity: Contains 1 thyroglobulin type-1 domain., subunit: Binds equally well IGF1 and IGF2.