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Atrophy is the partial or complete wasting
Wasting

In medical circles, wasting refers to the process by which a debilitating disease causes muscle and fat biological tissue to "waste" away. Wasting is sometimes referred to as "acute malnutrition" because it is believed that episodes of wasting have a short duration, in contrast to stunted growth, which is regarded as chronic malnutrition....
 away of a part of the body
Body

With regard to organism, a body is the integral physical material of an individual. "Body" often is used in connection with appearance, health issues and death....
. Causes of atrophy include poor nourishment, poor circulation
Circulatory system

The circulatory system is an organ that moves nutrients, gases, and wastes to and from cells to help fight diseases and help stabilize body temperature and pH to maintain homeostasis....
, loss of hormonal
Hormone

Hormones are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism....
 support, loss of nerve
Nerve

A nerve is an enclosed, cable-like bundle of Peripheral nervous system axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons....
 supply to the target organ
Organ (anatomy)

In biology, an organ is a biological tissue that performs a specific function or group of functions. Usually there is a main tissue and sporadic tissues....
, disuse or lack of exercise or disease intrinsic to the tissue itself. Hormonal and nerve inputs that maintain an organ or body part are referred to as trophic.

Atrophy is a general physiological process of reabsorption and breakdown of tissues
Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function....
, involving apoptosis
Apoptosis

Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Programmed Cell death involves a series of biochemical events leading to a characteristic cell Morphology and death, in more specific terms, a series of biochemical events that lead to a variety of morphological changes, including Bleb , changes...
 on a cell
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
ular level.






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Atrophy is the partial or complete wasting
Wasting

In medical circles, wasting refers to the process by which a debilitating disease causes muscle and fat biological tissue to "waste" away. Wasting is sometimes referred to as "acute malnutrition" because it is believed that episodes of wasting have a short duration, in contrast to stunted growth, which is regarded as chronic malnutrition....
 away of a part of the body
Body

With regard to organism, a body is the integral physical material of an individual. "Body" often is used in connection with appearance, health issues and death....
. Causes of atrophy include poor nourishment, poor circulation
Circulatory system

The circulatory system is an organ that moves nutrients, gases, and wastes to and from cells to help fight diseases and help stabilize body temperature and pH to maintain homeostasis....
, loss of hormonal
Hormone

Hormones are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism....
 support, loss of nerve
Nerve

A nerve is an enclosed, cable-like bundle of Peripheral nervous system axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons....
 supply to the target organ
Organ (anatomy)

In biology, an organ is a biological tissue that performs a specific function or group of functions. Usually there is a main tissue and sporadic tissues....
, disuse or lack of exercise or disease intrinsic to the tissue itself. Hormonal and nerve inputs that maintain an organ or body part are referred to as trophic.

Atrophy is a general physiological process of reabsorption and breakdown of tissues
Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function....
, involving apoptosis
Apoptosis

Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Programmed Cell death involves a series of biochemical events leading to a characteristic cell Morphology and death, in more specific terms, a series of biochemical events that lead to a variety of morphological changes, including Bleb , changes...
 on a cell
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
ular level. When it occurs as a result of disease
Disease

A disease or medical condition is an abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and Medical signs....
 or loss of trophic support due to other disease, it is termed pathological atrophy, although it can be a part of normal body development and homeostasis
Homeostasis

Homeostasis is the property of a system, either open system or closed system, that regulates its internal environment and tends to maintain a stable, constant condition....
 as well.

Atrophy examples


Normal development

Examples of atrophy as part of normal development include shrinking and involution of the thymus in early childhood and the tonsils in adolescence.

Muscle atrophies


Disuse atrophy of muscle
MUSCLE

MUSCLE is public domain, multiple sequence alignment software for protein and nucleotide sequences.MUSCLE is integrated into UGENE bioinformatics tool as a plugin....
s (muscle atrophy
Muscle atrophy

Muscle atrophy is defined as a decrease in the mass of the muscle; it can be a partial or complete wasting away of muscle. When a muscle atrophies, it becomes weaker, since the ability to exert force is related to mass; muscle atrophy is a co-morbidity of several common diseases, including cancer, AIDS, congestive heart disease, COPD , renal...
) and bone
Bone

Bones are rigid organ that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red blood cell and white blood cells and store minerals....
s, with loss of mass and strength, can occur after prolonged immobility, such as extended bedrest
Bedrest

Bedrest as a medicine treatment refers to staying in bed day and night as a treatment for an illness or medical condition, especially when prescribed or chosen rather than resulting from severe prostration or imminent death....
, or having a body part in a cast (living in darkness for the eye, bedridden for the legs etc.). This type of atrophy can usually be reversed with exercise unless severe. Astronauts in microgravity must exercise regularly to minimize atrophy of their limb muscles.

There are many diseases and conditions which cause atrophy of muscle mass. For example diseases such as cancer and AIDS induce a body wasting syndrome called "cachexia
Cachexia

Cachexia is weight loss, muscle atrophy, fatigue, weakness and significant anorexia in someone who is not actively trying to lose weight. It can be a sign of various underlying disorders; when a patient presents with cachexia, a doctor will generally consider the possibility of cancer, metabolic acidosis , certain infectious diseases , and...
", which is notable for the severe muscle atrophy
Muscle atrophy

Muscle atrophy is defined as a decrease in the mass of the muscle; it can be a partial or complete wasting away of muscle. When a muscle atrophies, it becomes weaker, since the ability to exert force is related to mass; muscle atrophy is a co-morbidity of several common diseases, including cancer, AIDS, congestive heart disease, COPD , renal...
 seen. Other syndromes or conditions which can induce skeletal muscle atrophy
Muscle atrophy

Muscle atrophy is defined as a decrease in the mass of the muscle; it can be a partial or complete wasting away of muscle. When a muscle atrophies, it becomes weaker, since the ability to exert force is related to mass; muscle atrophy is a co-morbidity of several common diseases, including cancer, AIDS, congestive heart disease, COPD , renal...
 are congestive heart failure
Congestive heart failure

Heart failure is a condition in which a problem with the structure or function of the heart impairs its ability to supply sufficient blood flow to meet the body's needs....
 and liver disease.

During aging, there is a gradual decrease in the ability to maintain skeletal muscle function and mass. This condition is called "sarcopenia
Sarcopenia

Sarcopenia is the degenerative loss of skeletal muscle mass and strength associated with aging....
", and may be distinct from atrophy in its pathophysiology. While the exact cause of sarcopenia is unknown, it may be induced by a combination of a gradual failure in the "satellite cells
Satellite cells

Satellite cells are small mononuclear progenitor cells with virtually no cytoplasm found in mature muscle. They are found sandwiched between the basement membrane and sarcolemma of individual muscle fibres, and can be difficult to distinguish from the sub-sarcolemmal nuclei of the fibres....
" which help to regenerate skeletal muscle fibers, and a decrease in sensitivity to or the availability of critical secreted growth factors which are necessary to maintain muscle mass and satellite cell survival.

Dystrophies, myosities, and motor neuron conditions

Pathologic atrophy of muscles can occur due to diseases of the motor nerves, or due to diseases of the muscle tissue itself. Examples of atrophying nerve diseases include CMT (Charcot Marie Tooth syndrome) poliomyelitis
Poliomyelitis

Poliomyelitis, often called polio or infantile paralysis, is an acute virus infectious disease spread from person to person, primarily via the fecal-oral route....
, amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis

Amyotrophic Lateral Sclerosis is a progressive, usually fatal, neurodegenerative disease caused by the degeneration of motor neurons, the nerve cells in the central nervous system that control voluntary muscle movement....
 (ALS or Lou Gehrig's disease), and Guillain-Barré syndrome
Guillain-Barré syndrome

Guillain-Barr? syndrome is an acute inflammatory demyelinating polyneuropathy , an Autoimmune Disease disease affecting the peripheral nervous system, usually triggered by an acute infectious process....
. Examples of atrophying muscle diseases include muscular dystrophy
Muscular dystrophy

Muscular dystrophy refers to a group of genetics, hereditary muscle diseases that weaken the muscles that move the human body. Muscular dystrophies are characterized by progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle cell and biological tissue....
, myotonia congenita
Myotonia congenita

Myotonia congenita is a genetic, neuromuscular disorder characterized by the slow relaxation of the muscles. Symptoms may include muscle stiffness and hypertrophy ....
, and myotonic dystrophy
Myotonic dystrophy

Myotonic dystrophy is a Chronic , slowly progressing, highly variable inherited multisystemic disease that can manifest at any age from birth to old age....
.

Gland atrophy

The adrenal gland
Adrenal gland

In mammals, the adrenal glands are the star-shaped endocrine glands that sit on top of the kidneys; their name indicates that position . They are chiefly responsible for regulating the stress response through the biosynthesis of corticosteroids and catecholamines, including cortisol and adrenaline, respectively....
s atrophy during prolonged use of exogenous glucocorticoid
Glucocorticoid

Glucocorticoids are a class of steroid hormones which bind to the glucocorticoid receptor , which is present in almost every animal cell.GCs are part of the feedback mechanism in the immune system which turns immune activity down....
s like prednisone
Prednisone

Prednisone is a synthetic corticosteroid drug that is usually taken orally but can be delivered by intramuscular injection and can be used for a number of different conditions....
. Atrophy of the breast
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....
s can occur with prolonged estrogen
Estrogen

Estrogens are a group of steroid compounds, named for their importance in the estrous cycle, and functioning as the primary female sex hormone....
 reduction, as with anorexia nervosa
Anorexia nervosa

Anorexia nervosa is a psychiatry illness that describes an eating disorder characterized by extreme low body weight and body image distortion with an obsessive fear of gaining weight....
 or menopause
Menopause

The Menopause is the permanent cessation of menstruation which occurs a considerable length of time before the end of the lifespan.The word was first applied to humans, and because of this it literally means the cessation of monthly cycles or menstrual cycles, from the Greek roots meno and pausis ....
. Atrophy of the testes occurs with prolonged use of enough exogenous sex steroid
Sex steroid

Sex steroids, also known as gonadal steroids, are steroid hormones that interact with vertebrate androgen or estrogen receptor s. Their effects are mediated by slow genomic mechanisms through nuclear receptors as well as by fast nongenomic mechanisms through membrane-associated receptors and signaling cascades....
 (either androgen
Androgen

Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors....
 or estrogen
Estrogen

Estrogens are a group of steroid compounds, named for their importance in the estrous cycle, and functioning as the primary female sex hormone....
) to reduce gonadotropin
Gonadotropin

Human Menopausal Gonadotropins are protein hormones secreted by gonadotrope cells of the pituitary gland of vertebrates.Gonadotropin is sometimes abbreviated Gn....
 secretion.

Vaginal atrophy

In post-menopausal women, the walls of the vagina become thinner. The mechanism for the age-related condition is not yet clear, though there are theories that the effect is caused by decreases in estrogen levels. This atrophy, and that of the breasts concurrently, is consistent with the homeostatic (normal development) role of atrophy in general, as after menopause the body has no further functional biological need to maintain the reproductive system which it has permanently shut down.

Research

It has been reported that Astemizole
Astemizole

Astemizole is a second generation antihistamine drug which has a long duration of action. Astemizole was discovered by Janssen Pharmaceutica in 1977....
 might prevent 97% of the muscle wasting that occurs in immobile, bedridden patients. Testing upon mice showed that it blocked the activity of a protein present in the muscle that is involved in muscle atrophy. However the concerns for the drug's longterm effects on the heart preclude its routine use in humans for this indication, and further alternative drugs are being sought.

See also

  • Olivopontocerebellar atrophy
    Olivopontocerebellar atrophy

    Olivopontocerebellar atrophy is a term used to define neuronal degeneration in the cerebellum, pontine nuclei, and inferior olivary nucleus. The use of the term has changed considerably in recent years due to the progressing knowledge of the genetic bases of the disease....
  • Optic atrophy
    Optic atrophy

    Optic atrophy is the loss of some or most of the fibers of the optic nerve. In medicine, "atrophy" usually means "shrunken but capable of regrowth", so some argue that "optic atrophy" as a pathological term is somewhat misleading and use "optic neuropathy" instead....
  • Spinomuscular atrophy
  • Testicular atrophy
    Testicular atrophy

    Testicular atrophy is a medical condition in which the male reproductive organ s diminish in size and may be accompanied by loss of function. This does not refer to temporary changes, such as those brought on by cold....
  • Hypertrophy
    Hypertrophy

    Hypertrophy is the increase of the size of an organ or in a select area of the tissue. It should be distinguished from hyperplasia which occurs due to cell division increasing the number of cells while their size stays the same; hypertrophy occurs due to an increase in the size of cells, while the number stays the same....