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Insulin-like growth factor 2 （IGF-2） is one of three protein hormones that share structural similarity to insulin. It has growth-regulating, insulin-like and mitogenic activities. It is believed to be a major fetal growth factor. The major role of IGF-2 is as a growth promoting hormone during gestation. IGF-2 exerts its effects by binding to the IGF-1 receptor and to the short isoform of the insulin receptor （IR-A or exon 11-）. IGF-2 may also bind to the IGF-2 receptor （also called the cation-independent mannose 6-phosphate receptor）, which acts as a signalling antagonist. IGF-2 acts as a co-hormone together with both FSH and LH. IGF-2 is sometimes produced in excess in islet cell tumors and non-islet hypoglycemic cell tumors, causing hypoglycemia. Loss of imprinting of IGF-2 is a common feature in tumors seen in Beckwith-Wiedemann syndrome. As IGF-2 promotes development of fetal pancreatic beta cells, it is believed to be related to some forms of diabetes mellitus.