GDNF and hyperinsulinism: Hyperinsulinemia leads to increased expression of insulin-like growth factor (IGF)-I expression, which is associated with tumor growth in vitro, in animal models, and in epidemiological studies in humans.[27] Basic research found glial cell line derived neurotrophic factor (GDNF) and its tyrosine kinase receptor RET expression in BxPC-3 and MIA PaCa-2 cells when exposed to different concentrations of glucose.[28] High glucose concentration was capable of accelerating tumorigenesis in humans.