Vasoinhibins are a family of peptides that inhibit blood vessel growth, dilation, permeability, and survival. They are generated by the proteolytic cleavage of prolactin by cathepsin D, matrix metalloproteases, and bone morphogenic protein-1. Lactotropes within the anterior pituitary gland produce and release vasoinhibins. Hypothalamic neurons within the supraoptic and paraventricular nuclei also synthesize prolactin and process it to vasoinhibins that are released locally or at the neurohypophyseal endings. While both the anterior and posterior pituitaries may function as sources of circulating vasoinhibins, these peptides could act as local regulators of pituitary gland functions including neovascularization and neurohypophyseal hormone release.