IGF1 and neoplasm: In an attempt to identify circulating factors that could help to explain the exacerbated tumor incidence observed in CORT-KO mice compared to control and SST-KO mice under normal conditions, we determined the plasma levels of a subset of hormones that could be involved in the development and progression of MG tumors, including GH and IGF-I [50], insulin [53], prolactin [54] and corticosterone [55].