MKI67 and pituitary apoplexy: The vascular endothelial growth factor, tumor necrosis factor-α (TNF-α), pituitary tumor-transforming gene (PTTG), matrix metalloproteinase-2/9 (MMP-2/9), proliferating marker (Ki-67), as well as hypoxia-inducing factor are the major contributing factors involved in pituitary apoplexy.