Hypothalamic–pituitary–prolactin axis peptide (VIP). Hypothalamic–pituitary–prolactin axis The hypothalamic–pituitary–prolactin axis (HPP axis), also known as the hypothalamic–pituitary–mammary axis or hypothalamic–pituitary–breast axis, is a hypothalamic–pituitary axis which includes the secretion of prolactin (PRL; luteotropin) from the lactotrophs of the pituitary gland into the circulation and the subsequent action of prolactin on tissues such as, particularly, the mammary glands or breasts. It is involved in lobuloalveolar maturation of the mammary glands during pregnancy and the induction and maintenance of lactation following parturition. Hormones that control the secretion of prolactin from the pituitary gland include dopamine ("prolactin-inhibiting factor", or "PIF"), estradiol, progesterone, thyrotropin-releasing hormone (TRH), and
Anterior pituitary death and can lead to gigantism, a hormone disorder shown in “giants” such as André the Giant, where it occurs before the epiphyseal plates in bones close in puberty. The most common type of pituitary tumour is a prolactinoma which hypersecretes prolactin. A third type of pituitary adenoma secretes excess ACTH, which in turn, causes an excess of cortisol to be secreted and is the cause of Cushing's disease. Hypopituitarism is characterized by a decreased secretion of hormones released by the anterior pituitary. For example, hypo-secretion of GH prior to puberty can be a cause of dwarfism. In addition, secondary