Vascular endothelial growth factor (VEGF) is encoded by VEGF gene, which contains 8 exons and maps to 6p21.3. It is a signal protein produced by cells that stimulates vasculogenesis and angiogenesis. Millauer et al. (1994) observed in mouse that its expression was upregulated by hypoxia and that its cell surface receptor, Flk1, is exclusively expressed in endothelial cells. Overexpression of VEGF can cause vascular disease in the retina of the eye and other parts of the body. Drugs such as bevacizumab can inhibit VEGF and control or slow those diseases. The VEGF is a candidate hormone for facilitating glucose passage across the blood-brain barrier under critical conditions.