Seattle Missing Persons Report, Auscycling Queensland Results, Windsor School District Salary Schedule, Articles P

Various hormones are secreted from the anterior pituitary during development and growth. Cai L, Wu ZR, Cao L, Xu JD, Lu JL, Wang CD, Jin JH, Wu ZB, Su ZP. - increase protein synthesis Prolactin plays an important role in maternal behavior. Preproopiomelanocortin (POMC) is a large polypeptide with a MW of 31,000 (265 aa). 1.) sharing sensitive information, make sure youre on a federal It is secreted heavily in pulses in between these events. [37], In humans, prolactin is produced at least in the anterior pituitary, decidua, myometrium, breast, lymphocytes, leukocytes and prostate.[38][39]. WebGrowth hormonereleasing hormone (GHRH) is the major stimulator and somatostatin is the major inhibitor of the synthesis and release of GH. sharing sensitive information, make sure youre on a federal The main action of prolactin is on the mammary glands to initiate and maintain lactation. high levels of blood glucose Ultimately dopamine, extrapituitary prolactin is controlled by a superdistal promoter and apparently unaffected by dopamine. 1.) Prolactin (PRL) was The putative Jak2/RUSH pathway is based on the fact that RUSH mediates the ability of PRL to augment progesterone-dependent gene transcription. It has important cell cycle-related functions as a growth-, differentiating- and anti-apoptotic factor. [17] Prolactin within the normal reference ranges can act as a weak gonadotropin, but at the same time suppresses gonadotropin-releasing hormone secretion. WebMelatonin is a hormone that your brain produces in response to darkness. Copyright 2023 Oxford University Press. WebThe hormones oxytocin and vasopressin (also known as ADH) are secreted from the posterior lobe of the pituitary. Characteristics of patients with diabetes insipidus are frequent urination and consumption of large volumes of water to prevent vascular collapse and dehydration. An example of the use of the above table is, if using the Centaur assay to estimate prolactin values in g/L for females, the mean is 7.92g/L and the reference range is 3.3516.4g/L. Most vertebrates, including humans, also have the closely related somatolactin. To purchase short-term access, please sign in to your personal account above. What 2 hormones produced by the anterior pituitary are single chain proteins? Growth hormone from both sources showed parallel dose-response displacement curves, by logit-log transformation, in both specific immunoassay and in a The hypthalamus contains osmole receptor neurons that respond to changes in the plasma NA+ concentration. WebAnswer to _____ hormone is produced by the anterior. prolactin Prolactin is the hormone that tells the body when to start making breast milk. Various drugs also influence the release of ADH. WebEvidence suggests that growth hormone and prolactin act by activating an associated protein kinase, which is the first step in the process of signal transduction. Hormones secreted by the anterior pituitary gland include adrenocorticotropin hormone (ACTH), growth hormone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), prolactin, and thyroid-stimulating hormone (TSH). -- sialic acid - acts as a protective coating and prevents degradation The cell bodies of the neurons in the hypothalamus produce releasing/inhibiting hormones that are transported via the portal vein vascular system to the anterior pituitary to either stimulate or inhibit the release of certain hormones. WebProlactin (PRL) and growth hormone (GH) act by way of their receptors as either hormones (systemically) or cytokines (locally). The hypothalamic hormones control the synthesis and release of the anterior pituitary hormones. These cells differentiate into oligodendrocytes, the cells responsible for the formation of myelin coatings on axons in the central nervous system. [28][29] Elevated levels of prolactin can inhibit hair growth,[30] and knock-out mutations in the prolactin gene cause increased hair length in cattle[31] and mice. Full lactation requires the actions of estrogen, progesterone, cortisol, GH and insulin. doi: 10.1128/MCB.00651-17. This site needs JavaScript to work properly. Bethesda, MD 20894, Web Policies Oxytocin causes contraction of the myoepithelial cells of alevoli in the breast to bring about "milk ejection" or "milk let down. Intracellular prolactin was equivalent to the amount secreted into medium in a period of about 1-2 hr. GH increases fat breakdown (lipolysis), increases plasma free fatty acids (FFAs) and decreases glucose uptake by adipose tissue, which prevents glucose from being converted into fat. Prolactin is sometimes classified as a gonadotropin[16] although in humans it has only a weak luteotropic effect while the effect of suppressing classical gonadotropic hormones is more important. Philadelphia: Saunders Elsevier; 185261, growth hormone receptor signaling pathway via JAK-STAT, positive regulation of receptor signaling pathway via JAK-STAT, regulation of multicellular organism growth, regulation of signaling receptor activity, negative regulation of endothelial cell proliferation, positive regulation of pri-miRNA transcription by RNA polymerase II, positive regulation of cell population proliferation, multicellular organismal response to stress, positive regulation of epithelial cell proliferation, WHO Expert Committee on Biological Standardization, GRCh38: Ensembl release 89: ENSG00000172179, GRCm38: Ensembl release 89: ENSMUSG00000021342, "Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice", "Morbid Obesity Due to Prolactinoma and Significant Weight Loss After Dopamine Agonist Treatment", "The biosynthesis of human growth hormone and prolactin", "Null mutation of the prolactin receptor gene produces a defect in maternal behavior", "Prolactin regulation of gonadotropin-releasing hormone neurons to suppress luteinizing hormone secretion in mice", "Prolactin receptor expression in human testis and accessory tissues: localization and function", "White matter plasticity and enhanced remyelination in the maternal CNS", "Why is sad music pleasurable? Diabetes insipidus results from a lack of ADH. IGF-2 acts in a paracrine fashion in the tissue to increase protein synthesis, RNA synthesis and DNA synthesis resulting in an increase in cell size and number. Prolactin also acts in a cytokine-like manner and as an important regulator of the immune system. prolactin and growth hormone are produced by Shibboleth / Open Athens technology is used to provide single sign-on between your institutions website and Oxford Academic. Give the BNAT exam to get a 100% scholarship for BYJUS courses, NCERT Solutions Class 12 Business Studies, NCERT Solutions Class 12 Accountancy Part 1, NCERT Solutions Class 12 Accountancy Part 2, NCERT Solutions Class 11 Business Studies, NCERT Solutions for Class 10 Social Science, NCERT Solutions for Class 10 Maths Chapter 1, NCERT Solutions for Class 10 Maths Chapter 2, NCERT Solutions for Class 10 Maths Chapter 3, NCERT Solutions for Class 10 Maths Chapter 4, NCERT Solutions for Class 10 Maths Chapter 5, NCERT Solutions for Class 10 Maths Chapter 6, NCERT Solutions for Class 10 Maths Chapter 7, NCERT Solutions for Class 10 Maths Chapter 8, NCERT Solutions for Class 10 Maths Chapter 9, NCERT Solutions for Class 10 Maths Chapter 10, NCERT Solutions for Class 10 Maths Chapter 11, NCERT Solutions for Class 10 Maths Chapter 12, NCERT Solutions for Class 10 Maths Chapter 13, NCERT Solutions for Class 10 Maths Chapter 14, NCERT Solutions for Class 10 Maths Chapter 15, NCERT Solutions for Class 10 Science Chapter 1, NCERT Solutions for Class 10 Science Chapter 2, NCERT Solutions for Class 10 Science Chapter 3, NCERT Solutions for Class 10 Science Chapter 4, NCERT Solutions for Class 10 Science Chapter 5, NCERT Solutions for Class 10 Science Chapter 6, NCERT Solutions for Class 10 Science Chapter 7, NCERT Solutions for Class 10 Science Chapter 8, NCERT Solutions for Class 10 Science Chapter 9, NCERT Solutions for Class 10 Science Chapter 10, NCERT Solutions for Class 10 Science Chapter 11, NCERT Solutions for Class 10 Science Chapter 12, NCERT Solutions for Class 10 Science Chapter 13, NCERT Solutions for Class 10 Science Chapter 14, NCERT Solutions for Class 10 Science Chapter 15, NCERT Solutions for Class 10 Science Chapter 16, NCERT Solutions For Class 9 Social Science, NCERT Solutions For Class 9 Maths Chapter 1, NCERT Solutions For Class 9 Maths Chapter 2, NCERT Solutions For Class 9 Maths Chapter 3, NCERT Solutions For Class 9 Maths Chapter 4, NCERT Solutions For Class 9 Maths Chapter 5, NCERT Solutions For Class 9 Maths Chapter 6, NCERT Solutions For Class 9 Maths Chapter 7, NCERT Solutions For Class 9 Maths Chapter 8, NCERT Solutions For Class 9 Maths Chapter 9, NCERT Solutions For Class 9 Maths Chapter 10, NCERT Solutions For Class 9 Maths Chapter 11, NCERT Solutions For Class 9 Maths Chapter 12, NCERT Solutions For Class 9 Maths Chapter 13, NCERT Solutions For Class 9 Maths Chapter 14, NCERT Solutions For Class 9 Maths Chapter 15, NCERT Solutions for Class 9 Science Chapter 1, NCERT Solutions for Class 9 Science Chapter 2, NCERT Solutions for Class 9 Science Chapter 3, NCERT Solutions for Class 9 Science Chapter 4, NCERT Solutions for Class 9 Science Chapter 5, NCERT Solutions for Class 9 Science Chapter 6, NCERT Solutions for Class 9 Science Chapter 7, NCERT Solutions for Class 9 Science Chapter 8, NCERT Solutions for Class 9 Science Chapter 9, NCERT Solutions for Class 9 Science Chapter 10, NCERT Solutions for Class 9 Science Chapter 11, NCERT Solutions for Class 9 Science Chapter 12, NCERT Solutions for Class 9 Science Chapter 13, NCERT Solutions for Class 9 Science Chapter 14, NCERT Solutions for Class 9 Science Chapter 15, NCERT Solutions for Class 8 Social Science, NCERT Solutions for Class 7 Social Science, NCERT Solutions For Class 6 Social Science, CBSE Previous Year Question Papers Class 10, CBSE Previous Year Question Papers Class 12, JEE Main 2022 Question Paper Live Discussion. WebPredict the changes in secretory rates of hypothalamic anterior pituitary and target gland hormones caused by oversecretion or undersecretion of any of these hormones or receptor deficit for any of these hormones. Diabetes mellitus has 2 types. Briefly describe how cell differentiation occurs in the developing animal embryo. Being exposed to light at night can block melatonin production. (Endocrinology100: 283, 1977). When to see a doctor See your doctor if you develop any of the signs and symptoms associated with hypopituitarism. Hormones 2004 Mar 10;294(1):269-80. doi: 10.1016/j.yexcr.2003.11.017. Acromegaly - hypersecretion of GH after closure of epiphyseal plate, GH deficiency in beginning in childhood that results in a reduced rate of growth, delayed skeletal and sexual maturation. Prolactinomas may disrupt the hypothalamic-pituitary-gonadal axis as prolactin tends to suppress the secretion of gonadotropin-releasing hormone from the hypothalamus and in turn decreases the secretion of follicle-stimulating hormone and luteinizing hormone from the anterior pituitary, therefore disrupting the ovulatory cycle. Vasopressor effect: Extracellular Vesicles: From Bone Development to Regenerative Orthopaedics. Responsivness to cAMP is mediated by an imperfect cAMPresponsive element and two CAAT/enhancer binding proteins (C/EBP). Increased osmolarity [Na+] increases ADH, whereas decreased osmolarity [Na+] decreases ADH. [64] Purified human prolactin was scarce, heterogeneous, unstable, and difficult to characterize. Anterior Pituitary Willams textbook of endocrinology. El Tahlawi SM, El Eishi NH, Kahhal RK, Hegazy RA, El Hanafy GM, Abdel Hay RM, Shaker OG. Increased fibrosis in white adipose tissue of male and female bGH transgenic mice appears independent of TGF- action, Disruption of RNA splicing is an important contributor to congenital hypopituitarism and other human genetic diseases, Berberine ameliorates obesity by inducing GDF15 secretion by brown adipocytes, Its Not Just for Pain: A New Metabolic Function of Aspirin, Volume 164, Issue 4, April 2023 (In Progress), The Journal of Clinical Endocrinology & Metabolism, Subscription prices and ordering for this journal, Purchasing options for books and journals across Oxford Academic, Receive exclusive offers and updates from Oxford Academic, Use of Antibodies to Sera of Hypophysectomized Animals in Pituitary Hormone Analysis and the Application of Landsteiner's Inhibition Test in Agar Gel Immunoassays, Further Studies on the Follicle-Stimulating Hormone-Releasing Action of Hypothalamic Extracts, A Study of the Immunological and Biological Properties of a Follicle-Stimulating Hormone, A New Sensitive Bio-ass ay for Follicle-Stimulating Hormone (FSH). The site is secure. [31][32] Additionally, prolactin delays hair regrowth in mice. 3. GH has an anti-insulin or "diabetogenic effects" in that it increases blood glucose levels, stimulates gluconeogenesis and inhibits the uptake of glucose by muscle and adipose. Treatment of diabetes insipidus is ADH which provides rapid relief. Their basic structure is: alpha subunit + beta subunit + CHO + sialic acid. Multilevel Differential Control of Hormone Gene Expression Programs by hnRNP L and LL in Pituitary Cells. Oxytocin. In one study, normal sperm characteristics were restored when prolactin levels were raised to normal values in hypoprolactinemic men.[69]. [61][62][63][64], The first International Reference Preparation (or IRP) of human Prolactin for Immunoassay was established in 1978 (75/504 1st IRP for human prolactin) at a time when purified human prolactin was in short supply. Increase lipolysis in adipose tissue. Melmed S, Kleinberg D 2008 Anterior pituitary. WebA prolactinoma is a type of pituitary tumor (adenoma) that produces an excessive amount of the hormone prolactin. They can act as classic endocrine modulators (hormones) via entry into the circulation or locally (cytokines) through juxtacrine, paracrine and autocrine modes of action. The purposes of oxytocin include facilitating uterine contractions during labor, allowing for milk let down during breastfeeding, promoting social bonding, and moderating testosterone levels. 2001 Jan 1;229(1):163-75. doi: 10.1006/dbio.2000.9961. Production of prolactin is controlled by two main hormones: dopamine and estrogen. Its primary function is to produce milk. Mayo Clinic GH has a MW of 22,000 (191 aa). -, Annu Rev Physiol. Growth is proportionate and not grotesque. 2018 May-Jun;63(3):241-245. doi: 10.4103/ijd.IJD_590_17. WebThe hormones oxytocin and vasopressin (also known as ADH) are secreted from the posterior lobe of the pituitary. Sex steroids at the time of puberty. 1997 Jan;2(1):7-17. doi: 10.1023/a:1026313211704. The exact mechanism by which it inhibits gonadotropin-releasing hormone is poorly understood. Nicotine, morphine, and barbiturates increase ADH to decrease urine output. Previous standards use other ratios. government site. The posterior lobe of the pituitary gland develops as an out pocketing of the hypothalamus, and so is composed of neural tissue. 1RW5, 2Q98, 3D48, 3EW3, 3MZG, 3N06, 3N0P, 3NCB, 3NCC, 3NCE, 3NCF, 3NPZ, Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals to produce milk. Prolactin and growth hormone signaling - PubMed The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). 1965 Sep;77(3):563-73 [40] A key regulator of prolactin production is estrogens that enhance growth of prolactin-producing cells and stimulate prolactin production directly, as well as suppressing dopamine. Oxytocin facilitates childbirth and lactation. [67][68][69] However, different assays and methods for measuring prolactin are employed by different laboratories and as such the serum reference range for prolactin is often determined by the laboratory performing the measurement. Careers. pituitary to inhibit the release of prolactin. Don't already have a personal account? ghrelin (stomach hormone produced during fasting) eCollection 2016. Enter your library card number to sign in. Bethesda, MD 20894, Web Policies Growth hormone from both sources showed parallel dose-response displacement curves, by logit-log transformation, in both specific immunoassay and in a specific lymphocyte binding assay. Try BYJUS free classes today! Print 2018 Jun 15. Downregulation of the growth hormone-induced Janus kinase 2/signal transducer and activator of transcription 5 signaling pathway requires an intact actin cytoskeleton. This study demonstrates that, prior to purification, tissue culture derived hormone can be characterized by multiple criteria and compared to a standard preparation. Weve got your back. What are the effects of osmolarity and blood volume on the release of ADH? Immunohistochemical markers of prognosis in adult granulosa cell tumors of the ovary - a review. Endocrine Accessibility The .gov means its official. [20], Other actions include contributing to pulmonary surfactant synthesis of the fetal lungs at the end of the pregnancy and immune tolerance of the fetus by the maternal organism during pregnancy. Would you like email updates of new search results? The primary stimulus for the release of prolactin is suckling by the baby. WebGrowth hormone (GH). Before What are 3 factors that inhibit the release of GH? WebGrowth hormone from both sources showed parallel dose-response displacement curves, by logit-log transformation, in both specific immunoassay and in a specific lymphocyte EndocrineWeb The suckling stimulus also triggers the release of oxytocin from the posterior pituitary gland, which triggers milk let-down: Prolactin controls milk production (lactogenesis) but not the milk-ejection reflex; the rise in prolactin fills the breast with milk in preparation for the next feed. Is patient hirsute or virilized yes prolactin normal Oxytocin has isoleucine & leucine at positions 3 & 8. The main stimulus for prolactin secretion is suckling, the effect of which is neuronally mediated. Control of growth hormone production by a clonal strain of rat pituitary cells. The relationship between serum levels of prolactin and growth MeSH The hormone acts in endocrine, autocrine, and paracrine manners through the prolactin receptor and numerous cytokine receptors.[5]. low levels of blood glucose 2018 May 29;38(12):e00651-17. [54][70] Furthermore, prolactin levels vary according to factors as age,[71] sex,[71] menstrual cycle stage[71] and pregnancy. ACTH - adrenocorticotropic hormone 3.) Muscle: Other hormones produced by the placenta The placenta also produces several other hormones including human placental lactogen and corticotrophin-releasing hormone. official website and that any information you provide is encrypted Gualtieri A, Kyprianou N, Gregory LC, Vignola ML, Nicholson JG, Tan R, Inoue SI, Scagliotti V, Casado P, Blackburn J, Abollo-Jimenez F, Marinelli E, Besser REJ, Hgler W, Karen Temple I, Davies JH, Gagunashvili A, Robinson ICAF, Camper SA, Davis SW, Cutillas PR, Gevers EF, Aoki Y, Dattani MT, Gaston-Massuet C. Nat Commun. Hormones The later action is most likely an indirect effect due to GH's lipolytic action to increase plasma FFAs. Stimulates gluconeogenesis in the liver ), figure (a): 8 product molecules GH does not exert all of these actions alone, but has synergistic actions with other hormones. [3] The protein encoded by this gene is a member of the somatotropin/prolactin family of hormones that play an important role in growth control. Sa-Nguanraksa D, Mitpakdi K, Samarnthai N, Thumrongtaradol T, O-Charoenrat P. Gland Surg. Activation also results in the activation of mitogen-activated protein kinases and Src kinase. Estrogen is necessary for the actions of oxytocin because estrogen increases oxytocin receptors. [57][58] Measurements that are calibrated against the current international standard can be converted into mass units using this ratio of grams to IUs;[60] prolactin concentrations expressed in mIU/L can be converted to g/L by dividing by 21.2. ADH (VP) and oxytocin are both composed of a 6 aa ring connected to a side chain of 3 aa. WebDopamine (a brain chemical) and estrogen (a hormone) control prolactin production and release from your pituitary gland. The false maintenance of pregnancy exhibits the outward physical symptoms of pregnancy, in the absence of a foetus. Prolactin values were obtained from specific control groups of varying sizes using the IMMULITE assay. It is influential in over 300 separate processes in various The anterior lobe is connected to the hypothalamus by a vascular system of portal veins between primary capillaries in the median eminence of the hypothalamus that receive systemic arterial flow and capillaries in the anterior lobe. Growth hormone and prolactin - SlideShare Which hormones are produced and released by posterior pituitary gland? Federal government websites often end in .gov or .mil. Additionally, prolactin is produced by adipose tissue and stimulates adipogenesis and inhibits lipolysis; it promotes insulin sensitivity [ 13 ]. Epinephrine, caffeine, and alcohol inhibit ADH, which increases urine output. Many mammals experience a seasonal cycle. Excitation of the hypothalamic nuclei is coupled to their secretion by the posterior pituitary gland. Prolactin is a hormone produced by the pituitary gland that stimulates growth and regulates metabolism. WebENDOCRINOLOGY 358 Clinical Presentation Symptoms Decreased libido Hot flashes if testosterone loss is sudden Signs Sparse facial and body hair Gynecomastia Small penis, prostate, and testes Related conditions Infertility Osteoporosis If hypogonadal during adolescence, may have complete failure of sexual maturation Absence of growth spurt, One of the main regulators of the production of prolactin from the pituitary gland is the hormone called dopamine, which is produced by the hypothalamus, the part of the brain directly above the pituitary gland. Dopamine restrains prolactin production, so the more dopamine there is, the less prolactin is released. Endocrinology. The posterior lobe is an out-pocketing of the hypothalamus and connected via neural tissue. Prolactin - an overview | ScienceDirect Topics What are some neural factors that influence the secretion of prolactin? 2005 Mar;20(3):313-8. doi: 10.1007/s00467-004-1713-8. Structure, Synthesis, Secretion, and Target Cells of the Hypothalamic Releasing Hormones: E. Hypothalamic Control of Prolactin Secretion", "Prolactin expression and secretion by human breast glandular and adipose tissue explants", "333 Disorders of the Anterior Pituitary and Hypothalamus", "The approach to patients with "non-epileptic seizures", "Etiology, diagnosis, and treatment of secondary amenorrhea", "Prolactin Biology and Laboratory Measurement: An Update on Physiology and Current Analytical Issues", "Prolactin synthesized and secreted by human peripheral blood mononuclear cells: an autocrine growth factor for lymphoproliferation", "Human prolactin receptors are insensitive to mouse prolactin: implications for xenotransplant modeling of human breast cancer in mice", "WHO Expert Committee on Biological Standardization", "WHO International Standard, Prolactin, Human. Type 2 usually onsets in adulthood. Type 2 diabetes mellitus is known as non-insulin dependent diabetes mellitus and is caused by obesity. The sucking activates mechanoreceptors in and around the nipple. 2016 Oct 5;11(10):e0164131. Growth hormone and prolactin--molecular and functional Access to content on Oxford Academic is often provided through institutional subscriptions and purchases. A possible role for prolactin", "The role of prolactin in fish reproduction", "Association of polymorphisms for prolactin and prolactin receptor genes with broody traits in chickens", "Prolactin and Its Receptor Are Expressed in Murine Hair Follicle Epithelium, Show Hair Cycle-Dependent Expression, and Induce Catagen", "Prolactin Signaling Influences the Timing Mechanism of the Hair Follicle: Analysis of Hair Growth Cycles in Prolactin Receptor Knockout Mice", "Human scalp hair follicles are both a target and a source of prolactin, which serves as an autocrine and/or paracrine promoter of apoptosis-driven hair follicle regression", "Functionally reciprocal mutations of the prolactin signalling pathway define hairy and slick cattle", "Convergent Evolution of Slick Coat in Cattle through Truncation Mutations in the Prolactin Receptor", "Early and late feathering in turkey and chicken: same gene but different mutations", "Extrapituitary prolactin: distribution, regulation, functions, and clinical aspects", "Prolactin in man: a tale of two promoters", "III. Please enable it to take advantage of the complete set of features! Click the account icon in the top right to: Oxford Academic is home to a wide variety of products. Prolactin is available commercially for use in other animals, but not in humans. Explain why oil and water do not mix. Suppose the reaction is carried out at two temperatures as shown below. Prolactin stimulates T and B cells, natural killer cells, macrophages, neutrophils, CD34+ hematopoietic cells, and antigen presenting dendritic cells [ 12 ]. It is produced in the neurosecretory cells of the hypothalamus. Right on! The amino acid sequences differ only in positions 3 & 8. This mating can cause bi-daily surges of prolactin which would normally occur in rodent pregnancy. We conclude that multifunctional rat pituitary cells in culture show unusual promise for further studies of the control of expression of organ-specific activities in mammalian cells. What are 6 neural inputs that stimulate the release of GH? 1973 Oct;93(4):793-9. doi: 10.1210/endo-93-4-793. 2003-2023 Chegg Inc. All rights reserved. WebProlactin hormone, formed by the pituitary gland, is the most vital hormone in our body. [5] Prolactin is secreted from the pituitary gland in response to eating, mating, estrogen treatment, ovulation and nursing. [25] In the South American discus, prolactin may also regulate the production of a skin secretion that provides food for larval fry. It stimulates the mammary glands to produce milk (lactation): increased serum concentrations of prolactin during pregnancy cause enlargement of the mammary glands and prepare for milk production, which normally starts when levels of progesterone fall by the end of pregnancy and a suckling stimulus is present.