Prolactin - Podcast Version TeachMePhysiology 0:00 / 0:00 1x 0.25x 0.5x 0.75x 1x 1.25x 1.5x 1.75x 2x Prolactin is one of the hormones produced by the anterior pituitary gland. It is particularly important in breast development and production of breast milk during pregnancy and breastfeeding. In this article, we will look at the production and regulation of prolactin, along with its physiological functions and related clinical conditions. Pro Feature - 3D Model You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Prolactin Production Prolactin (PRL) is produced by lactotroph cells in the anterior pituitary gland. Unlike many other anterior pituitary hormones, prolactin secretion is primarily controlled by inhibition rather than stimulation from the hypothalamus. Functions of Prolactin The main physiological functions of prolactin are related to pregnancy and lactation. During pregnancy, gradually increasing prolactin levels act alongside oestrogen and progesterone to promote breast development. The main actions of prolactin include: Initiation of milk production by alveolar cells (lactogenic effect) Maintenance of milk production after lactation has started (galactopoietic effect) Proliferation and growth of alveolar and duct cells (mammogenic effect) Prolactin’s most important physiological roles are the lactogenic and galactopoietic effects involved in breastfeeding. Oxytocin is also involved in breastfeeding by stimulating milk ejection from the breast, whereas prolactin primarily stimulates milk production. Rajendra prabhune, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons Fig 1Diagram showing the structure of a lactating breast Regulation of Prolactin Secretion Prolactin release is inhibited by dopamine (DA), and is therefore known, in this context, as prolactin inhibitory factor (PIF). Suckling is the strongest physiological stimulus for prolactin release. Stimulation of the nipple sends signals via afferent neural pathways through the spinal cord. These signals inhibit dopaminergic neurons in the hypothalamus. Since, dopamine normally suppresses prolactin secretion, this process increases prolactin release through a processes called disinhibition. Thyrotropin-releasing hormone (TRH), produced by the hypothalamus, also stimulates prolactin secretion. Furthermore, oestrogen increases the sensitivity of lactotroph cells to TRH, while also reducing their sensitivity to dopamine inhibition. Created in https://BioRender.com Fig 2Diagram showing the regulation of prolactin secretion Note: the prolactin axis does not technically have a negative feedback system. Without inhibition by dopamine, prolactin would be secreted indefinitely. Clinical Relevance Breastfeeding and Ovarian Cycles Lactation commonly suppresses normal ovarian cycles after pregnancy. This occurs because prolactin reduces gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus. Reduced GnRH secretion decreases follicle-stimulating hormone (FSH) and luteinising hormone (LH) release, therefore suppressing ovulation. Breastfeeding will not indefinitely cease ovarian cycles. Cycles eventually resume even if breastfeeding continues. If the mother does not breastfeed the infant, ovulatory cycles will usually resume within 8-10 weeks after delivery. Clinical Relevance Hyperprolactinaemia Hyperprolactinaemia refers to abnormally elevated prolactin levels. Common clinical features include: Menstrual disturbances such as amenorrhoea or oligomenorrhoea Galactorrhoea (milk discharge unrelated to breastfeeding) Hypogonadism, which can cause infertility, erectile dysfunction and osteoporosis The causes of hyperprolactinaemia can be remembered using the 5 Ps: Physiological Breastfeeding, stress, transient rises after intercourse Pregnancy Due to increased oestrogen stimulation of prolactin secretion Pharmacological Particularly dopamine antagonists, such as antipsychotic medications Prolactinoma A prolactin-secreting pituitary tumour Polycystic Ovarian Syndrome (PCOS) The mechanism is not exactly known but is thought to be related to increased oestrogen stimulation of prolactin secretion Management involves identifying and treating the underlying cause. Do you think you’re ready? Take the quiz below Pro Feature - Quiz Prolactin Question 1 of 3 Submitting... Skip Next Rate question: You scored 0% Skipped: 0/3 More Questions Available Upgrade to TeachMePhysiology Pro Challenge yourself with over 2100 multiple-choice questions to reinforce learning Learn More Rate This Article