Significance During embryogenesis, a dense vascular network develops in the pituitary gland through the process of angiogenesis. In tandem, pituitary gland precursor cells differentiate into hormone-producing cells that will rely on the vasculature to carry out regulated endocrine function. Our data show that expression of the cell surface adhesion molecule, integrin β1, in the epithelial-derived precursor cells is required for development of the vasculature and coordinated terminal differentiation of endocrine cells.