D R Grattan The hypothalamo-prolactin axis 226:2 T101–T122 Thematic Review Open Access 60 YEARS OF NEUROENDOCRINOLOGY The hypothalamo-prolactin axis David R Grattan1,2 Correspondence should be addressed 1Centre for Neuroendocrinology and Department of Anatomy, University of Otago, to D R Grattan PO Box 913, Dunedin 9054, New Zealand Email 2Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, New Zealand
[email protected] Abstract The hypothalamic control of prolactin secretion is different from other anterior pituitary Key Words hormones, in that it is predominantly inhibitory, by means of dopamine from the tubero- " prolactin infundibular dopamine neurons. In addition, prolactin does not have an endocrine target " tuberoinfundibular tissue, and therefore lacks the classical feedback pathway to regulate its secretion. Instead, dopamine neurons it is regulated by short loop feedback, whereby prolactin itself acts in the brain to stimulate " pregnancy production of dopamine and thereby inhibit its own secretion. Finally, despite its relatively " lactation simplename, prolactin has a broad range offunctions in the body,in addition to its defining role " prolactin-releasing factor in promoting lactation. As such, the hypothalamo-prolactin axis has many characteristics that are quite distinct from other hypothalamo-pituitary systems. This review will provide a brief overview of our current understanding of the neuroendocrine control of prolactin secretion, in particular focusing on the plasticity evident in this system, which keeps prolactin secretion at low levels most of the time, but enables extended periods of hyperprolactinemia when Journal of Endocrinology necessary for lactation. Key prolactin functions beyond milk production will be discussed, particularly focusing on the role of prolactin in inducing adaptive responses in multiple different systems to facilitate lactation, and the consequences if prolactin action is impaired.