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. Binds IGF2 more than IGF1. Detected in adult ewe, liver > kidney > lung >> heart and also in several fetal tissues. There are two different molecular mass variants (29 kDa and 24 kDa forms). The 29 kDa form was shown to be N-glycosylated.