HMGA2 and pituitary gland adenoma: Over-expression of either Hmga1 or Hmga2 resulted in the development of mixed somatotroph/lactotroph pituitary adenomas by 16 months of age (Fedele et al., 2005, Fedele et al., 2002), and Hmga2 has been reported to enhance E2F1 activity, which is usually repressed by Rb to prevent progression through the cell cycle (Fedele et al., 2006).