Estrogen could bind to its nuclear receptor, stimulating secretions of various growth factors such as Insulin-like Growth Factor (IGF), epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF), thereby activating Extracellular signal-regulated kinases (ERK), a signaling pathway to promote endothelial and ovarian proliferation, and even cancer formation (Driggers & Segars, 2002). Here, IGF1 is linked to cancer.