Hyperplasia
Encyclopedia
Hyperplasia means increase in number of cells/proliferation of cells. It may result in the gross enlargement
of an organ and the term is sometimes mixed with benign neoplasia
/ benign tumor.
Hyperplasia is a common preneoplastic response to stimulus. Microscopically cells resemble normal cells but are increased in numbers. Sometimes cells may also be increased in size (hypertrophy
). Hyperplasia is different from hypertrophy
in that the adaptive cell change
in hypertrophy is an increase in cell size, whereas hyperplasia involves an increase in the number of cells.
(normal) response to a specific stimulus, and the cells of a hyperplastic growth remain subject to normal regulatory control mechanisms. This stands in contrast to neoplasia
(the process underlying cancer
and benign tumors), in which genetically abnormal cells
proliferate in a non-physiological manner which is unresponsive to normal stimuli.
As seen in examples below, such physiological proliferation of cells may in fact be secondarily
due to a pathological cause. Still, the proliferation itself is a normal response to another abnormal condition, in contrast to neoplasia, where the proliferation in itself is abnormal.
or disease
elsewhere. 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 gland
ular cells in the breast
as a response to pregnancy
, thus preparing for future breast feeding.
Hyperplasia may also be induced artificially by injecting hormone
s such as IGF-1 and human growth hormone.
Perhaps the most interesting and potent effect IGF has on the human body is its ability to cause hyperplasia, which is an actual splitting of cells. By contrast, hypertrophy
is what occurs, for example, to skeletal muscle cells during weight training
and steroid use and is simply an increase in the size of the cells. With IGF use, one is able to cause hyperplasia which actually increases the number of muscle cells present in the tissue. Weight training with or without anabolic steroid
use enables these new cells to mature in size and strength. In addition, animal tests have shown that stretching a muscle can trigger hyperplasia, though this phenomenon has yet to be confirmed in humans. 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.
Hyperplasia may also occur abnormally, and is associated with a variety of clinical diseases.
Gross anatomy
Gross anatomy is the study of anatomy at the macroscopic level. The term gross distinguishes it from other areas of anatomical study, including microscopic anatomy, which is studied on a microscopic scale, typically with a microscope....
of an organ and the term is sometimes mixed with benign neoplasia
Neoplasia
Neoplasm is an abnormal mass of tissue as a result of neoplasia. Neoplasia is the abnormal proliferation of cells. The growth of neoplastic cells exceeds and is not coordinated with that of the normal tissues around it. The growth persists in the same excessive manner even after cessation of the...
/ benign tumor.
Hyperplasia is a common preneoplastic response to stimulus. Microscopically cells resemble normal cells but are increased in numbers. Sometimes cells may also be increased in size (hypertrophy
Hypertrophy
Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It should be distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number...
). Hyperplasia is different from hypertrophy
Hypertrophy
Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It should be distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number...
in that the adaptive cell change
Cellular adaptation
In cell biology and pathophysiology, cellular adaptation refers to changes made by a cell in response to adverse environmental changes. The adaptation may be physiologic or pathologic . Five major types of adaptation include atrophy, hypertrophy, hyperplasia, dysplasia, and metaplasia.Atrophy is a...
in hypertrophy is an increase in cell size, whereas hyperplasia involves an increase in the number of cells.
Difference from neoplasia
Hyperplasia is considered to be a physiologicalPhysiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
(normal) response to a specific stimulus, and the cells of a hyperplastic growth remain subject to normal regulatory control mechanisms. This stands in contrast to neoplasia
Neoplasia
Neoplasm is an abnormal mass of tissue as a result of neoplasia. Neoplasia is the abnormal proliferation of cells. The growth of neoplastic cells exceeds and is not coordinated with that of the normal tissues around it. The growth persists in the same excessive manner even after cessation of the...
(the process underlying cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
and benign tumors), in which genetically abnormal cells
Carcinogenesis
Carcinogenesis or oncogenesis is literally the creation of cancer. It is a process by which normal cells are transformed into cancer cells...
proliferate in a non-physiological manner which is unresponsive to normal stimuli.
As seen in examples below, such physiological proliferation of cells may in fact be secondarily
Comorbidity
In medicine, comorbidity is either the presence of one or more disorders in addition to a primary disease or disorder, or the effect of such additional disorders or diseases.- In medicine :...
due to a pathological cause. Still, the proliferation itself is a normal response to another abnormal condition, in contrast to neoplasia, where the proliferation in itself is abnormal.
Causes
Hyperplasia may be due to any number of causes, including increased demand (for example, proliferation of basal layer of epidermis to compensate skin loss), chronic inflammatory response, hormonal dysfunctions, or compensation for damageInjury
-By cause:*Traumatic injury, a body wound or shock produced by sudden physical injury, as from violence or accident*Other injuries from external physical causes, such as radiation injury, burn injury or frostbite*Injury from infection...
or disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
elsewhere. 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 gland
Gland
A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface .- Types :...
ular cells in the breast
Breast
The breast is the upper ventral region of the torso of a primate, in left and right sides, which in a female contains the mammary gland that secretes milk used to feed infants.Both men and women develop breasts from the same embryological tissues...
as a response to pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
, thus preparing for future breast feeding.
Hyperplasia may also be induced artificially by injecting hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s such as IGF-1 and human growth hormone.
Perhaps the most interesting and potent effect IGF has on the human body is its ability to cause hyperplasia, which is an actual splitting of cells. By contrast, hypertrophy
Hypertrophy
Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It should be distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number...
is what occurs, for example, to skeletal muscle cells during weight training
Weight training
Weight training is a common type of strength training for developing the strength and size of skeletal muscles. It uses the weight force of gravity to oppose the force generated by muscle through concentric or eccentric contraction...
and steroid use and is simply an increase in the size of the cells. With IGF use, one is able to cause hyperplasia which actually increases the number of muscle cells present in the tissue. Weight training with or without anabolic steroid
Anabolic steroid
Anabolic steroids, technically known as anabolic-androgen steroids or colloquially simply as "steroids", are drugs that mimic the effects of testosterone and dihydrotestosterone in the body. They increase protein synthesis within cells, which results in the buildup of cellular tissue ,...
use enables these new cells to mature in size and strength. In addition, animal tests have shown that stretching a muscle can trigger hyperplasia, though this phenomenon has yet to be confirmed in humans. 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.
Hyperplasia may also occur abnormally, and is associated with a variety of clinical diseases.
Examples in human biology and disease
Some of the more commonly-known clinical forms of hyperplasia, or conditions leading to hyperplasia, are:- Benign prostatic hyperplasiaBenign prostatic hyperplasiaBenign prostatic hyperplasia also known as benign prostatic hypertrophy , benign enlargement of the prostate , and adenofibromyomatous hyperplasia, refers to the increase in size of the prostate....
, also known as prostate enlargement. - Cushing's diseaseCushing's diseaseCushing's disease is a cause of Cushing's Syndrome characterised by increased secretion of adrenocorticotropic hormone from the anterior pituitary. This is most often as a result of a pituitary adenoma...
– Physiopathology of hyperplasia of adrenal cortex due to increased circulating level of ACTH (adrenocorticotropic hormone). - Congenital adrenal hyperplasiaCongenital adrenal hyperplasiaCongenital adrenal hyperplasia refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands ....
- Endometrial hyperplasiaEndometrial hyperplasiaEndometrial hyperplasia is a condition of excessive proliferation of the cells of the endometrium, or inner lining of the uterus.Most cases of endometrial hyperplasia result from high levels of estrogens, combined with insufficient levels of the progesterone-like hormones which ordinarily...
– Hyperproliferation of the endometrium, usually in response to unopposed estrogenEstrogenEstrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...
stimulation in the setting of polycystic ovary syndromePolycystic ovary syndromePolycystic ovary syndrome is one of the most common female endocrine disorders. PCOS is a complex, heterogeneous disorder of uncertain aetiology, but there is strong evidence that it can to a large degree be classified as a genetic disease....
or exogenous administration of hormones. Atypical endometrial hyperplasia may represent an early neoplastic processNeoplasiaNeoplasm is an abnormal mass of tissue as a result of neoplasia. Neoplasia is the abnormal proliferation of cells. The growth of neoplastic cells exceeds and is not coordinated with that of the normal tissues around it. The growth persists in the same excessive manner even after cessation of the...
which can lead to endometrial adenocarcinomaEndometrial cancerEndometrial cancer refers to several types of malignancies that arise from the endometrium, or lining, of the uterus. Endometrial cancers are the most common gynecologic cancers in the United States, with over 35,000 women diagnosed each year. The incidence is on a slow rise secondary to the...
. - Hemihyperplasia when only half (or one side) of the body is affected, sometimes generating limbs of different lengths.
- Hyperplasia of the breast – "Hyperplastic" lesions of the breastBreastThe breast is the upper ventral region of the torso of a primate, in left and right sides, which in a female contains the mammary gland that secretes milk used to feed infants.Both men and women develop breasts from the same embryological tissues...
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. The biology of these lesions is the subject of dispute, with some authorities arguing that both of these lesions are the result of neoplasiaNeoplasiaNeoplasm is an abnormal mass of tissue as a result of neoplasia. Neoplasia is the abnormal proliferation of cells. The growth of neoplastic cells exceeds and is not coordinated with that of the normal tissues around it. The growth persists in the same excessive manner even after cessation of the...
, and that the application of the term "hyperplasia" in this instance is "inaccurate." - Intimal hyperplasiaIntimal hyperplasiaIntimal hyperplasia is 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...
– The thickening of the Tunica intimaTunica intimaThe tunica intima is the innermost layer of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina...
of a blood vessel as a complication of a reconstruction procedure or endarterectomyEndarterectomyEndarterectomy is a surgical procedure to remove the atheromatous plaque material, or blockage, in the lining of an artery constricted by the buildup of soft/hardening deposits. It is carried out by separating the plaque from the arterial wall....
. 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. - 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 papillomavirusHuman papillomavirusHuman papillomavirus is a member of the papillomavirus family of viruses that is capable of infecting humans. Like all papillomaviruses, HPVs establish productive infections only in keratinocytes of the skin or mucous membranes...
(HPV). Heck's disease has not been known to cause cancer. - Sebaceous hyperplasiaSebaceous hyperplasiaSebaceous hyperplasia is a disorder of the sebaceous glands in which they become enlarged.producing yellow, shiny bumps on the face. These bumps are a natural response to the maternal hormones of pregnancy and usually resolve on their own within a few weeks after delivery.Sebaceous glands are...
– In this condition, small yellowish growths develop on the skin, usually on the face. This condition is neither contagious nor dangerous. - Compensatory liverLiverThe liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
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 hepatocyteHepatocyteA hepatocyte is a cell of the main tissue of the liver. Hepatocytes make up 70-80% of the liver's cytoplasmic mass.These cells are involved in:* Protein synthesis* Protein storage* Transformation of carbohydrates...
division, i.e., hyperplasia. This is the basis for living-donor liver transplants.