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Pituitary Dwarfism

Pituitary dwarfism

Definition

Dwarfism is a condition in which the growth of the individual is very slow or delayed, resulting in less than normal adult stature. The word pituitary refers to the pituitary gland, which regulates the production of certain chemicals called hormones. Therefore, pituitary dwarfism is decreased bodily growth due primarily to hormonal problems. The end result is a proportionate little person, because the height and the growth of all other structures of the individual are decreased.

Description

Pituitary dwarfism is caused by problems arising from the pituitary gland. The pituitary gland, also called the hypophysis, is a gland at the base of the brain that produces many different hormones. This gland is divided into the anterior (front) and posterior (back) halves. The anterior pituitary produces six hormones: growth hormone, adrenocorticotropin (corticotropin), thyroid stimulating hormone (thyrotropin), prolactin, follicle stimulating hormone, and lutenizing hormone. The posterior pituitary gland only produces two hormones: antidiuretic hormone (vasopressin) and oxytocin.

The growth process begins in the lower part of the forebrain in a small organ called the hypothalamus. The hypothalamus releases hormones that regulate the production of other hormones. When the hypothalamus releases growth hormone-releasing hormone (GHRH), the anterior pituitary is stimulated to release growth hormone (GH). Growth hormone then acts on the liver and other tissues and stimulates them to secrete insulin-like growth factor-1 (IGF-1). IGF-1 directly promotes the development of bone and muscle, causing bones to grow in length, and muscles to increase protein synthesis (make more protein).

Since growth is a complex phenomenon, it may be slowed down or stopped by abnormalities arising at any point in the process. Thus, dwarfism can result if there is a deficiency in any of these hormones, if there is a failure in the receptor cells receiving the hormonal stimuli, or if the target cells are unable to respond.

At its most basic, pituitary dwarfism results from decreased production of hormones by the anterior pituitary. When none of the hormones of the anterior pituitary are adequately produced, this is called panhypopituitarism. A common form of pituitary dwarfism is due to deficiencies in the production of growth hormone (GH). When less GH than normal is produced during childhood, an individual's arms, legs, and other structures continue to develop in normal proportions, but at a decreased rate.

Demographics

It is estimated that between one in 14,000 and one in 27,000 babies born each year have some form of dwarfism. In 2004, more than 20,000 children in United States were receiving supplemental GH therapy. It is estimated that about one quarter of them had organic causes of GH deficiencies. There appears to be no racial or ethnic component to pituitary dwarfism, but males seem to be afflicted more than females.

Causes and symptoms

Investigations are underway to determine the specific genetic mutations that can cause dwarfism. Pituitary dwarfism can be caused by:

  • genetics
  • accident-related trauma to the pituitary gland
  • surgical injury of the pituitary
  • central nervous system tumor
  • central nervous system trauma
  • central nervous system radiation
  • leukemia

In most cases, the cause of dwarfism is not known (idiopathic).

A child with a growth hormone deficiency is often small with an immature face and chubby body build. The child's growth does not follow the normal growth curve patterns. In cases of tumor, most commonly craniopharyngioma (a tumor near the pituitary gland), children and adolescents may have neurological symptoms such as headaches, vomiting , and problems with vision. The child may also have symptoms of double vision. The symptom, however, that all children with pituitary dwarfism share is that they do not grow at the same rate as their peers.

When to call the doctor

If a child appears to be smaller than children two or more years younger than he or she is, the doctor should be consulted.

Diagnosis

Growth hormone deficiency is present at birth, but since the primary symptoms of pituitary dwarfism are height and growth at a reduced rate, the condition is not diagnosed until later in childhood. Charting a child's growth in comparison to age norms will help lead to a diagnosis. Another diagnostic technique uses an x ray of the child's hand to determine the child's bone age by comparing this to the child's actual chronological age. The bone age in affected children is usually two or more years behind the chronological age. This means that if a child is 10 years old, his or her bones will look like they are those of an eight-year-old. The levels of growth hormone and IGF-1 may also be measured with blood tests.

The doctor will do a complete examination to make sure that delayed growth is not caused by other underlying problems, such as tumor. X rays of the area where the pituitary gland is located, or more advanced imaging such as magnetic resonance imaging (MRI) or computed tomography (CT), may help the doctor make a diagnosis and may show whether there have been any changes to the pituitary gland itself.

Treatment

Growth hormone replacement therapy can be administered if the child is lacking growth hormone. A pediatric endocrinologist, a doctor specializing in the hormones of children, administers this type of therapy before a child's bone growth plates have fused or joined. Once the growth plates have fused, GH replacement therapy is rarely effective.

Until 1985, growth hormone was obtained from the pituitary glands of human cadavers. However, some disease complications resulted, and the United States Food and Drug Administration (FDA) banned this source of GH. In 1985, recombinant DNA techniques produced a safe and unlimited supply of GH in the lab. Now, the only growth hormone used for treatment is that which is made in a laboratory.

If growth hormone is not the only hormone deficiency, the doctor must prescribe ways to raise the levels of the other deficient hormones, if these options are available. A careful balancing of all of the hormones produced by the pituitary gland is necessary for patients with panhypopituitarism, making this form of dwarfism complex and difficult to manage.

Prognosis

The prognosis depends on the cause of the dwarfism. A panhypopituitarism dwarf does not pass through the initial onset of adult sexual development (puberty ) and never produces enough gonadotropic (sex) hormones to develop adult sexual function. These individuals also have other medical conditions that may prove fatal. Dwarfism due only to growth hormone deficiency has a much better prognosis if treated early with replacement GH. These individuals do pass through puberty and mature sexually; however, without treatment, they remain proportionately small in stature.

The success of treatment with GH varies. An increase in height of 46 in. (1015 cm) can occur in the first year of treatment. Following this first year, the response to the hormone replacement therapy is less pronounced. Even after this first year, however, the child usually continues to grow at a faster rate than he or she would without GH therapy. Long-term use is considered successful if the individual grows at least 0.75 in. (2 cm) per year more than he or she would without the hormone. However, if GH therapy is not given before the growth plates of the long bonessuch as the legs and armsfuse, the individual will not grow. Prognosis is generally better the earlier a child starts GH replacement therapy.

Improvement for individuals with other causes of dwarfism, such as a tumor, varies greatly. The prognosis usually depends on successful resolution of the underlying problem, whether there is any permanent damage, and the age of the child.

Prevention

There is no known way to prevent pituitary dwarfism, although in some cases it may be caused by traumatic injury to the pituitary gland. Engaging in safe behaviors may reduce the risk of injury-induced pituitary deficiencies.

Parental concerns

Children with pituitary dwarfism are smaller than other children, but they are just as smart and can lead long, healthy lives. It is important for parents not to expect less of their child with pituitary dwarfism simply because the child looks younger than he or she actually is. Chores and conversations should be appropriate to the actual age of the child. Children with pituitary dwarfism may face thoughtless comments from others on occasion, and the parents' reaction to such comments can strongly determine how the child feels about himself or herself.

KEY TERMS

Adrenocorticotropic hormone (ACTH) Also called adrenocorticotropin or corticotropin, this hormone is produced by the pituitary gland to stimulate the adrenal cortex to release various corticosteroid hormones.

Antidiuretic hormone (ADH) Also called vasopressin, a hormone that acts on the kidneys to regulate water balance.

Craniopharyngioma A tumor near the pituitary gland in the craniopharyngeal canal that often results in intracranial pressure.

Deprivational dwarfism A condition where emotional disturbances are associated with growth failure and abnormalities of pituitary function.

Follicle-stimulating hormone (FSH) A pituitary hormone that in females stimulates the ovary to mature egg capsules (follicles) and in males stimulates sperm production.

Growth hormone A hormone that eventually stimulates growth. Also called somatotropin.

Hormone A chemical messenger secreted by a gland or organ and released into the bloodstream. It travels via the bloodstream to distant cells where it exerts an effect.

Luteinizing hormone A hormone secreted by the pituitary gland that regulates the menstrual cycle and triggers ovulation in females. In males it stimulates the testes to produce testosterone.

Oxytocin A hormone that stimulates the uterus to contract during child birth and the breasts to release milk.

Panhypopituitarism Generalized decrease of all of the anterior pituitary hormones.

Prolactin A hormone that helps the breast prepare for milk production during pregnancy.

Puberty The point in development when the ability to reproduce begins. The gonads begin to function and secondary sexual characteristics begin to appear.

Thyroid-stimulating hormone (TSH) A hormone produce by the pituitary gland that stimulates the thyroid gland to produce the hormones that regulate metabolism. Also called thyrotropin.

Resources

BOOKS

Ghigo, C. et al, eds. Growth Hormone Secretagogues. New York: Elsevier, 1999.

Melmed, Shlomo, ed. The Pituitary. Malden, MA: Blackwell Pub., 2002.

PERIODICALS

Klotter, Jule. "Growth Hormone Replacement Therapy." Townsend Letter for Doctors and Patients 251 (June 2004): 28.

"Message to Parents: Hold Off on Growth Hormone for Short Kids." Life Science Weekly (Sept. 14, 2004): 1172.

Sandberg, David E. et al. "Height and Social Adjustment: are Extremes a Cause for Concern and Action?" Pediatrics 114, no. 3 (Sept. 2004): 74451.

ORGANIZATIONS

Human Growth Foundation. 997 Glen Cove Avenue, Suite 5 Glen Head, NY 11545. (800) 451-6434 Fax: (516) 671-4055 <www.hgfound.org>

Little People of America, Inc. 5289 NE Elam Young Parkway, Suite F-700 Hillsboro, OR 97124. (888) LPA-2001 or (530) 846-1562 Fax: (503) 846-1590. <www.plaonline.org.org>

Tish Davidson, A.M. Jason S. Schliesser, D.C.

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"Pituitary Dwarfism." Gale Encyclopedia of Children's Health: Infancy through Adolescence. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

"Pituitary Dwarfism." Gale Encyclopedia of Children's Health: Infancy through Adolescence. . Encyclopedia.com. (December 11, 2017). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/pituitary-dwarfism

"Pituitary Dwarfism." Gale Encyclopedia of Children's Health: Infancy through Adolescence. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/pituitary-dwarfism

Pituitary Dwarfism

Pituitary Dwarfism

Definition

Dwarfism is a condition in which the growth of the individual is very slow or delayed. There are many forms of dwarfism. The word pituitary is in reference to the pituitary gland in the body. This gland regulates certain chemicals (hormones) in the body. Therefore, pituitary dwarfism is decreased bodily growth due to hormonal problems. The end result is a proportionate little person, because the height as well as the growth of all other structures of the individual are decreased.

Description

Pituitary dwarfism is caused by problems arising in the pituitary gland. The pituitary gland is also called the hypophysis. The pituitary gland is divided into two halves: the anterior (front) and posterior (back) halves. The anterior half produces six hormones: growth hormone, adrenocorticotropin (corticotropin), thyroid stimulating homone (thyrotropin), prolactin, follicle stimulating hormone, and lutenizing hormone. The posterior pituitary gland only produces two hormones. It produces antidiuretic hormone (vasopressin) and oxytocin.

Most forms of dwarfism are a result of decreased production of hormones from the anterior half of the pituitary gland. The most common form is due to decreases of growth hormone which will be discussed here. These decreases during childhood cause the individual's arms, legs, and other structures to develop normal proportions for their bodies, but at a decreased rate.

When all of the hormones of the anterior pituitary gland are not produced, this is called panhypopituitarism. Another type of dwarfism occurs when only the growth hormone is decreased. Dwarfism can also result from a lack of somatomedin C (also called insulin like growth factor, IGF-1) production. Somatomedin C is a hormone produced in the liver that increases bone growth when growth hormone is present. The African pygmy and the Levi-Lorain dwarfs lack the ability to produce somatomedin C in response to growth hormone. All causes of dwarfism lead to a proportionate little person.

Growth is the body's response to different hormones. The forebrain contains a small organ called the hypothalamus, which is responsible for releasing hormones in response to the body's needs for purposes of regulation. Growth hormone is produced in the anterior pituitary gland when growth hormone-releasing hormone (GHRH), is released by the hypothalamus. Growth hormone is then released and stimulates the liver to produce IGF-1. In return, IGF-1 stimulates the long bones to grow in length. Thus, growth can be slowed down or stopped if there is a problem making any of these hormones or if there is a problem with the cells receiving these hormones.

Some estimates show that there are between 10,000 and 15,000 children in the United States who have growth problems due to a deficiency of growth hormone.

Causes and symptoms

Pituitary dwarfism has been shown to run in families. New investigations are underway to determine the specific cause and location of the gene responsible for dwarfism. The human cell contains 46 chromosomes arranged in 23 pairs. Most of the genes in the two chromosomes of each pair are identical or almost identical with each other. However, with dwarfism, there appears to be disruption on different areas of chromosome 3 and 7. Some studies have isolated defects for the production of pituitary hormones to the short arm (the "p" end) of chromosome 3 at a specific location of 3p11. Other studies have found changes on the short arm of chromosome 7.

A child with a growth hormone deficiency is often small with an immature face and chubby body build. The child's growth will slow down and not follow the normal growth curve patterns. In cases of tumor, most commonly craniopharyngioma (a tumor near the pituitary gland), children and adolescents may present with neurological symptoms such as headaches, vomiting, and problems with vision. The patient may also have symptoms of double vision. Symptoms such as truly bizarre and excessive drinking behaviors (polydipsia) and sleep disturbances may be common.

Diagnosis

The primary symptom of pituitary dwarfism is lack of height. Therefore, a change in the individual's growth habits will help lead to a diagnosis. Another diagnostic technique uses an x ray of the child's hand to determine the child's bone age by comparing this to the child's actual chronological age. The bone age in affected children is usually two years or more behind the chronological age. This means that if a child is ten years old, his or her bones will look like they are those of an eight-year-old child. The levels of growth hormone and somatomedin C must also be measured with blood tests.

Hypopituitarism may be gained or acquired following birth for several reasons. It could be due to trauma to the pituitary gland such as a fall or following surgery to the brain for removal of a tumor. It may also be due to the child's environment (deprivational dwarfism).

On examination by the doctor there may be optic nerve atrophy, if the dwarfism is due to a type of tumor. X rays of the area where the pituitary gland is located (sella turcica) or more advanced imaging such as magnetic resonance imaging (MRI) or computed tomography CT may show changes of the pituitary gland itself. Computed tomography, is an advanced form of x ray that will help determine the integrity of the bone and how much calcification the tumor is producing. Magnetic resonance imaging, will also help in the diagnosis. MRI is a type of imaging device that can visualize soft tissues such as muscle and fat.

If the dwarfism is due to environmental and emotional problems, the individual may be hospitalization to monitor hormone levels. Following a few days of hospitalized, hormone levels may become normal due to avoidance of the original environment.

Treatment

The main course of therapy is growth hormone replacement therapy when there is lack of growth hormone in the body. A pediatric endocrinologist, a doctor specializing in the hormones of children, usually administers this type of therapy before a child's growth plates have fused or joined together. Once the growth plates have fused, GH replacement therapy is rarely effective.

Growth hormone used to be collected from recently deceased humans. However, frequent disease complications resulting from human growth hormone collected from deceased bodies, lead to the banning of this method. In the mid-1980s, techniques were discovered that could produce growth hormones in the lab. Now, the only growth hormone used for treatment is that made in a laboratory.

A careful balancing of all of the hormones produced by the pituitary gland is necessary for patients with panhypopituitarism. This form of dwarfism is very difficult to manage.

Prognosis

The prognosis for each type of dwarfism varies. A panhypopituitarism dwarf does not pass through the initial onset of adult sexual development (puberty ) and never produces enough gonadotropic hormones to develop adult sexual function. These individuals also have several other medical conditions. Dwarfism due to only growth hormone deficiency has a different prognosis. These individuals do pass through puberty and mature sexually, however, they remain proportionately small in stature.

If the individual is lacking only growth hormone then growth hormone replacement therapy can be administered. The success of treatment with growth hormone varies however. An increase in height of 4-6 in (10-15 cm) can occur in the first year of treatment. Following this first year, the response to the hormone is not as successful. Therefore the amount of growth hormone administered must be tripled to maintain this rate. Long-term use is considered successful if the individual grows at least 0.75 in (2 cm) per year more than they would without the hormone. However, if the growth hormone treatment is not administered before the long bonessuch as the legs and armsfuse, then the individual will never grow. This fusion is completed by adult age.

Improvement for individuals with dwarfism due to other causes such as a tumor, varies greatly. If the dwarfism is due to deprevational causes, then removing a child from that environment should help to alleviate the problem.

KEY TERMS

Adrenocorticotropin (corticotrophin) A hormone that acts on cells of the adrenal cortex, causing them to produce male sex hormones and hormones that control water and mineral balance in the body.

Antidiuretic hormone (vasopressin) A hormone that acts on the kidneys to regulate water balance.

Craniopharyngioma A tumor near the pituitary gland in the craniopharyngeal canal that often results in intracranial pressure.

Deprivational dwarfism A condition where emotional disturbances are associated with growth failure and abnormalities of pituitary function.

Follicle-stimulating hormone (FSH) A hormone that in females stimulates estrogen and in males stimulates sperm production.

Growth hormone A hormone that eventually stimulates growth. Also called somatotropin.

Hormone A chemical messenger produced by the body that is involved in regulating specific bodily functions such as growth, development, and reproduction.

Luteinizing hormone A hormone secreted by the pituitary gland that regulates the menstrual cycle and triggers ovulation in females. In males it stimulates the testes to produce testosterone.

Oxytocin A hormone that stimulates the uterus to contract during child birth and the breasts to release milk.

Panhypopituitarism Generalized decrease of all of the anterior pituitary hormones.

Prolactin A hormone that helps the breast prepare for milk production during pregnancy.

Puberty Point in development when the gonads begin to function and secondary sexual characteristics begin to appear.

Thyroid stimulating hormone (thyrotropin) A hormone that stimulates the thyroid gland to produce hormones that regulate metabolism.

Resources

BOOKS

Beers, Mark H., Robert Berkow, and Mark Burs. "Pituitary Dwarfism." In MerckManual. Rahway, NJ: Merck & Co., Inc., 2004.

ORGANIZATIONS

Human Growth Foundation. 997 Glen Cove Ave., Glen Head, NY 11545. (800) 451-6434. Fax: (516) 671-4055. http://www.hgfound.org.

Little People of America, Inc. National Headquarters, PO Box 745, Lubbock, TX 79408. (806) 737-8186 or (888) LPA-2001. lpadatabase@juno.com. http://www.lpaonline.org.

OTHER

"Clinical Growth Charts by the National Center for Health Statistics." Center for Disease Control. http://www.cdc.gov/nchs/about/major/nhanes/growthcharts/clinical_charts.htm.

"Entry 312000: Panhypopituitarism; PHP." OMIMOnline Mendelian Inhericance in Man. National Institutes of Health. http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?312000.

Hill, Mark. "Development of the Endocrine SystemPituitary." The University of New South Wales, Sydney, AustraliaDepartment of Embryology. http://anato-my.med.unsw.edu.au/CBL/Embryo/OMIMfind/endocrine/pitlist.htm.

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"Pituitary Dwarfism." Gale Encyclopedia of Medicine, 3rd ed.. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

"Pituitary Dwarfism." Gale Encyclopedia of Medicine, 3rd ed.. . Encyclopedia.com. (December 11, 2017). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/pituitary-dwarfism-0

"Pituitary Dwarfism." Gale Encyclopedia of Medicine, 3rd ed.. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/pituitary-dwarfism-0