Prolactin is a peptide hormone primarily associated with lactation. It is synthesized and secreted by lactotrope cells in the adenohypophysis (anterior pituitary gland). It is also produced in other tissues including the breast and the decidua. Pituitary prolactin secretion is regulated by neuroendocrine neurons in the hypothalamus, most importantly by neurosecretory dopamine neurons of the arcuate nucleus, which inhibit prolactin secretion. Prolactin antibody is a useful marker in classification of pituitary tumors and the study of pituitary disease. It reacts with lactotrope cells.^1-2