Hyperplasia (or "hypergenesis") is a general term referring to the proliferation of cells within an
organIn biology and anatomy, an organ is a collection of tissues joined in structural unit to serve a common function ....
or tissue beyond that which is ordinarily seen (e.g. constantly dividing cells). Hyperplasia may result in the
gross enlargementGross 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 must be studied with the aid of a microscope.-Techniques of study:...
of an organ, the formation of a benign tumor, or may be visible only upon histological analysis with a
microscopeA microscope is an instrument to see objects too tiny for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.-History:An early microscope was made in 1590 in Middelburg, The...
. Hyperplasia is different from
hypertrophyHypertrophy 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 changeIn 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.
Hyperplasia (or "hypergenesis") is a general term referring to the proliferation of cells within an
organIn biology and anatomy, an organ is a collection of tissues joined in structural unit to serve a common function ....
or tissue beyond that which is ordinarily seen (e.g. constantly dividing cells). Hyperplasia may result in the
gross enlargementGross 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 must be studied with the aid of a microscope.-Techniques of study:...
of an organ, the formation of a benign tumor, or may be visible only upon histological analysis with a
microscopeA microscope is an instrument to see objects too tiny for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.-History:An early microscope was made in 1590 in Middelburg, The...
. Hyperplasia is different from
hypertrophyHypertrophy 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 changeIn 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 is the science of the functioning of living systems. It is a subcategory of biology...
(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
neoplasiaNeoplasm is an abnormal mass of tissue as a result of neoplasia.Neoplasia is the abnormal proliferation of cells. The growth of this clone of cells exceeds, and is uncoordinated with, that of the normal tissues around it. It usually causes a lump or tumor...
(the process underlying
cancerCancer is a class of diseases in which a group of cells display uncontrolled growth , invasion , and sometimes metastasis...
and some benign tumors), in which
genetically abnormal cellsCarcinogenesis , is the process by which normal cells are transformed into cancer cells.Cell division is a physiological process that occurs in almost all tissues and under many circumstances...
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
secondarilyIn 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....
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, chronic inflammatory response, hormonal dysfunctions, or
compensationCompensatory growth is a type of regenerative growth that can take place a number of human organs after the organs are either damaged, removed, or cease to function. The growth can be a result of increased cell size or an increase in cell division . For instance, if one kidney is removed, the...
for
damageInjury or bodily injury is damage or harm caused to the structure or function of the body caused by an outside agent or force, which may be physical or chemical, and either by accident or intentional. Personal Injury also refers to damage caused to the reputation of another rather than physical...
or
diseaseA disease or medical condition isan abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and signs...
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
glandA gland is an organ in an animal's body that synthesizes a substance for release 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
breastThe breast is the upper ventral region of an animal’s torso, particularly that of mammals, including human beings. The breasts of a female primate’s body contain the mammary glands, which secrete milk used to feed infants....
as a response to
pregnancyPregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the uterus of a female. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets. Human pregnancy is the most studied of all mammalian pregnancies. Obstetrics is the surgical field...
, thus preparing for future breast feeding.
Hyperplasia may also be induced artificially by injecting
hormoneA hormone is a chemical released by one or more cells that affects cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms...
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.
HypertrophyHypertrophy 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...
, on the other hand, is what occurs during
weight trainingWeight training is a common type of strength training for developing the strength and size of skeletal muscles. It uses the 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 muscle cells. With IGF use, one is able to cause this hyperplasia which actually increases the number of muscle cells present in the tissue. Weight training with or without
anabolic steroidAnabolic steroids, or anabolic-androgenic steroids , are a class of steroid hormones related to the hormone testosterone. They increase protein synthesis within cells, which results in the buildup of cellular tissue , especially in muscles...
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:
- Cushing's disease - Physiopathology of hyperplasia of adrenal cortex due to increased circulating level of ACTH (adrenocorticotropic hormone).
- Congenital adrenal hyperplasia
Congenital 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 hyperplasia
Endometrial 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 estrogenEstrogens are a group of steroid compounds, named for their importance in the estrous cycle, and functioning as the primary female sex hormone, their name comes from estrus/oistros + gen/gonos = to generate.Estrogens are used as part of some oral contraceptives, in estrogen replacement...
stimulation in the setting of polycystic ovary syndromePolycystic ovary syndrome is an endocrine disorder that affects approximately 5% of all women.It occurs amongst all races and nationalities, is the most common hormonal disorder among women of reproductive age, and is a leading cause of infertility.The principal features are obesity, anovulation ,...
or exogenous administration of hormones. Atypical endometrial hyperplasia may represent an early neoplastic processNeoplasm is an abnormal mass of tissue as a result of neoplasia.Neoplasia is the abnormal proliferation of cells. The growth of this clone of cells exceeds, and is uncoordinated with, that of the normal tissues around it. It usually causes a lump or tumor...
which can lead to endometrial adenocarcinomaEndometrial cancer refers to several types of malignancy which 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 in the U.S...
.
- Benign prostatic hyperplasia
Benign 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 in middle-age and elderly men...
, also known as prostate enlargement.
- Hyperplasia of the breast - "Hyperplastic" lesions of the breast
The breast is the upper ventral region of an animal’s torso, particularly that of mammals, including human beings. The breasts of a female primate’s body contain the mammary glands, which secrete milk used to feed infants....
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 neoplasiaNeoplasm is an abnormal mass of tissue as a result of neoplasia.Neoplasia is the abnormal proliferation of cells. The growth of this clone of cells exceeds, and is uncoordinated with, that of the normal tissues around it. It usually causes a lump or tumor...
, and that the application of the term "hyperplasia" in this instance is "inaccurate."
- Intimal hyperplasia
Intimal 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 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 endarterectomyEndarterectomy 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 movements 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 papillomavirus
A human papillomavirus is a papillomavirus that infects the epidermis and mucous membranes of humans. HPV can lead to cancers of the cervix, vulva, vagina, and anus in women. In men, it can lead to cancers of the anus and penis....
(HPV). Heck's disease has not been known to cause cancer.
- Sebaceous hyperplasia
Sebaceous hyperplasia is a disorder of the sebaceous glands in which they become enlarged. These glands are located within the skin and are responsible for secreting an oily substance named sebum. They are commonly associated with hair follicles but they can be found in hairless regions of the skin...
- In this condition, small yellowish growths develop on the skin, usually on the face. This condition is neither contagious nor dangerous.
- Compensatory liver
The 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 hepatocyteHepatocytes make up 70-80% of the cytoplasmic mass of the liver.These cells are involved in protein synthesis, protein storage and transformation of carbohydrates, synthesis of cholesterol, bile salts and phospholipids, and detoxification, modification and excretion of exogenous and endogenous...
division, i.e., hyperplasia. This is the basis for living-donor liver transplants.