Hyperplasia#Examples in human biology and disease

Hyperplasia may be due to any number of causes, including proliferation of basal layer of epidermis to compensate skin loss, chronic inflammatory response, hormonal dysfunctions, or compensation for damage or disease elsewhere.{{Cite book |title = Essentials of Pathophysiology: Concepts of Altered Health States |url = https://books.google.com/books?id=FFg88IaReBwC&pg=PA775 |publisher = Lippincott Williams & Wilkins |date = 2011 |isbn = 978-1-58255-724-3 |vauthors = Porth C }} Hyperplasia may be harmless and occur on a particular tissue. An example of a normal hyperplastic response would be the growth and multiplication of milk-secreting glandular cells in the breast as a response to pregnancy, thus preparing for future breast feeding.{{Cite book |title = Breast Surgical Techniques and Interdisciplinary Management |url = https://books.google.com/books?id=ICfEsoKSwmsC&pg=PA188 |publisher = Springer Science & Business Media |date = January 2011 |isbn = 978-1-4419-6076-4 |vauthors = Dirbas F, Scott-Conner C }}

One of the most potent and noteworthy effects insulin-like growth factor 1 (IGF-1) has on the human body is its ability to cause hyperplasia, which is an actual splitting of cells.{{Cite book |title = Advanced Neuromuscular Exercise Physiology |url = https://books.google.com/books?id=tTaLY-JpsJsC&pg=PA146 |publisher = Human Kinetics |isbn = 978-1-4504-1227-8 |vauthors = Gardiner P}} By contrast, hypertrophy is what occurs, for example, to skeletal muscle cells during weight resistance training and is simply an increase in the size of the cells.{{Cite book |title = The Young Athlete: A Sports Doctor's Complete Guide for Parents |url = https://books.google.com/books?id=56QJzCNEjzkC&pg=PT126 |publisher = Little, Brown |date = October 2009 |isbn = 978-0-316-08673-8 |vauthors = Metzl JD, Shookhoff C}} With IGF-1 use, one is able to cause hyperplasia which actually increases the number of muscle cells present in the tissue.{{Cite book |title = The Endocrine System |veditors = Rodgers K |url = https://books.google.com/books?id=JemcAAAAQBAJ&pg=PA45 |publisher = Britannica Educational Publishing |date = November 2011 |isbn = 978-1-61530-731-9}} Weight training enables these new cells to mature in size and strength. It is theorized that hyperplasia may also be induced through specific power output training for athletic performance, thus increasing the number of muscle fibers instead of increasing the size of a single fiber.{{Cite book |title = Therapeutic Exercise: Foundations and Techniques |url = https://books.google.com/books?id=udY-AAAAQBAJ&pg=PA169 |publisher = F.A. Davis |date = December 2012 |isbn = 978-0-8036-3897-6 |vauthors = Kisner C, Colby LA}}

Hyperplasia is considered to be a physiological (normal) response to a specific stimulus, and the cells of a hyperplastic growth remain subject to normal regulatory control mechanisms. However, hyperplasia can also occur as a pathological response, if an excess of hormone or growth factor is responsible for the stimuli. Similarly to physiological hyperplasia, cells that undergo pathologic hyperplasia are controlled by growth hormones, and cease to proliferate if such stimuli are removed.{{Cite book|title=Robbins Basic Pathology| vauthors = Kumar V, Abbas A, Aster J |publisher=Elsevier|year=2013|isbn=978-0-8089-2432-6|location=Philadelphia, US|pages=4}} This differs from neoplasia (the process underlying cancer and benign tumors), in which genetically abnormal cells manage to proliferate in a non-physiological manner which is unresponsive to normal stimuli.{{Cite book|title = Holland Frei Cancer Medicine Eight|url = https://books.google.com/books?id=R0FbhLsWHBEC&pg=PA26 |publisher = PMPH-USA|date = 2010|isbn = 978-1-60795-014-1 | vauthors = Hong WK, Hait WN }} That being said, the effects caused by pathologic hyperplasia can provide a suitable foundation from which neoplastic cells may develop.

Hyperplasia of certain tissues may cause disease. Pathologic hyperplasia in these tissues may occur due to infection, physiological stress or trauma, or abnormal levels of particular hormones, such as estrogen, ACTH, or cortisol.{{Cite web | vauthors = Kemp WL, Burns DK, Brown TG |title= Pathology: The Big Picture | work = AccessMedicine | publisher = McGraw Hill Medical |url=https://accessmedicine.mhmedical.com/book.aspx?bookid=499&isMissingChapter=true |access-date=2021-12-06 }}

Some of the more commonly known clinical forms of hyperplasia, or conditions leading to hyperplasia, include:

• Benign prostatic hyperplasia, also known as prostate enlargement.{{Cite web|title = Prostate Enlargement (Benign Prostatic Hyperplasia) |url = https://www.niddk.nih.gov/health-information/urologic-diseases/prostate-problems/prostate-enlargement-benign-prostatic-hyperplasia | work = National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) | publisher = U.S. Department of Health and Human Services National Institutes of Health |access-date = 2015-05-30}}
• Cushing's disease – Physiopathology of hyperplasia of adrenal cortex due to increased circulating level of ACTH (adrenocorticotropic hormone).{{Cite encyclopedia|title = Cushing disease | encyclopedia = MedlinePlus Medical Encyclopedia | publisher = National Library of Medicine, U.S. Department of Health and Human Services National Institutes of Health |url = https://www.nlm.nih.gov/medlineplus/ency/article/000348.htm |access-date = 2015-05-30}}
• Congenital adrenal hyperplasia – Inherited disorder of gland (adrenal).{{Cite encyclopedia|title = Congenital adrenal hyperplasia | encyclopedia = MedlinePlus Medical Encyclopedia | publisher = National Library of Medicine, U.S. Department of Health and Human Services National Institutes of Health |url = https://www.nlm.nih.gov/medlineplus/ency/article/000411.htm |access-date = 2015-05-30}}
• Endometrial hyperplasia – Hyperproliferation of the endometrium, usually in response to unopposed estrogen stimulation in the setting of polycystic ovary syndrome or exogenous administration of hormones. Atypical endometrial hyperplasia may represent an early neoplastic process which can lead to endometrial adenocarcinoma.{{Cite web|title = Endometrial Hyperplasia |url = http://www.acog.org/Patients/FAQs/Endometrial-Hyperplasia| work = American College of Obstetricians and Gynecologists (ACOG) |access-date = 2015-05-30}} The development of endometrial adenocarcinoma from endometrial hyperplasia is a typical example of how the effects of pathologic hyperplasia can lead to neoplasia, and females who exhibit hyperplasia of the endometrium are indeed more likely to develop cancer of these cells.

File:Hemihyper.jpg can be noted by the pelvic tilt.]]

• Hemihyperplasia – When only half (or one side) of the body is affected, sometimes generating limbs of different lengths.{{Cite web|title = Hemihyperplasia - Glossary Entry|url = http://ghr.nlm.nih.gov/glossary=hemihyperplasia| work = Genetics Home Reference | publisher = National Library of Medicine, U.S. Department of Health and Human Services |access-date = 2015-05-30}}
• Hyperplasia of the breast – "Hyperplastic" lesions of the breast include usual ductal hyperplasia, a focal expansion of the number of cells in a terminal breast duct, and atypical ductal hyperplasia, in which a more abnormal pattern of growth is seen, and which is associated with an increased risk of developing breast cancer.{{Cite book|title = Diagnostic Problems in Breast Pathology|url = https://books.google.com/books?id=W2BzkJwU21kC&pg=PA33 |publisher = Elsevier Health Sciences|date = 2009|isbn = 978-1-4160-2612-9 | vauthors = Koerner FC }}
• Intimal hyperplasia – The thickening of the tunica intima of a blood vessel as a complication of a reconstruction procedure or endarterectomy. Intimal hyperplasia is the universal response of a vessel to injury and is an important reason of late bypass graft failure, particularly in vein and synthetic vascular grafts.{{cite journal | vauthors = Subbotin VM | title = Analysis of arterial intimal hyperplasia: review and hypothesis | journal = Theoretical Biology & Medical Modelling | volume = 4 | pages = 41 | date = October 2007 | pmid = 17974015 | pmc = 2169223 | doi = 10.1186/1742-4682-4-41 | doi-access = free }}
• Focal epithelial hyperplasia (also known as Heck's disease) – This is a wart-like growth in the mucous tissues of the mouth or, rarely, throat that is caused by certain sub-types of the human papillomavirus (HPV). Heck's disease has not been known to cause cancer.{{Cite book|title = Essentials of Oral Pathology|url = https://books.google.com/books?id=fDRtoGmVGQQC&pg=PA9 |publisher = JP Medical Ltd|date = 2011|isbn = 9789350252147 | vauthors = Purkait SK }}
• Myofibre hyperplasia (also known as double-muscling) – seen in cattle, genetic mutations cause large muscles due to increased proliferation of myofibres and decreased adipose tissue.{{Cite journal |last=Swatland |first=Howard |date=January 1974 |title=Developmental disorders of skeletal muscle in cattle, pigs and sheep |url=https://www.researchgate.net/publication/233398466 |journal=The Veterinary Bulletin |volume=44 |issue=4 |pages=187–189 |via=ResearchGate}}
• Sebaceous hyperplasia – In this condition, small yellowish growths develop on the skin, usually on the face. This condition is neither contagious nor dangerous.{{Cite book|title = Skin Diseases in the Elderly: A Color Handbook|url = https://books.google.com/books?id=fPMoxcB2XDwC&pg=PA85 |publisher = CRC Press|date = October 2011 |isbn = 978-1-84076-615-8 | vauthors = Evans CC, High WA }}
• Compensatory liver hyperplasia – The liver undergoes cellular division after acute injury, resulting in new cells that restore liver function back to baseline. Approximately 75% of the liver can be acutely damaged or resected with seemingly full regeneration through hepatocyte division, i.e., hyperplasia. This is what makes living-donor liver transplants possible.{{Cite book|title = Robbins & Cotran Pathologic Basis of Disease|url = https://books.google.com/books?id=5NbsAwAAQBAJ&pg=PA36 |publisher = Elsevier Health Sciences|date = September 2014 |isbn = 978-0-323-29635-9 | vauthors = Kumar V, Abbas AK, Aster JC }}
• Epidermal hyperplasia of the skin{{citation needed|date=February 2020}}

• List of biological development disorders
• Hyperplasia of midface

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• {{Cite book|title = Benign Prostatic Hyperplasia and Lower Urinary Tract Symptoms in Men|url = https://books.google.com/books?id=WP6g0PSD1Y8C |publisher = OUP Oxford|date = 2011-11-24|isbn = 978-0-19-957277-9 | vauthors = Bachmann A, de la Rosette J }}

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Category:Anatomical pathology