The pituitary gland or hypothesis is a small gland about 1 centimeter in diameter or the size of a pea. It is nearly surrounded by bone as it rests in the sella turcica, a depression in the sphenoid bone. The gland is connected to the hypothalamus of the brain by a slender stalk called the infundibulum.
There are two distinct regions in the gland: the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis). The activity of the adenohypophysis is controlled by releasing hormones from the hypothalamus. The neurohypophysis is controlled by nerve stimulation.
Hormones of the Anterior Lobe (Adenohypophysis)
Growth hormone is a protein that stimulates the growth
of bones, muscles, and other organs by promoting protein
synthesis. This hormone drastically affects the
appearance of an individual because it influences
height. If there is too little growth hormone in a
child, that person may become a pituitary dwarf of
normal proportions but small stature. An excess of the
hormone in a child results in an exaggerated bone
growth, and the individual becomes exceptionally tall or
Thyroid-stimulating hormone, or thyrotropin, causes the
glandular cells of the thyroid to secrete thyroid
hormone. When there is a hypersecretion of
thyroid-stimulating hormone, the thyroid gland enlarges
and secretes too much thyroid hormone.
Hormones of the Posterior Lobe (Neurohypophysis)
Antidiuretic hormone promotes the reabsorption of water by the kidney tubules, with the result that less water is lost as urine. This mechanism conserves water for the body. Insufficient amounts of antidiuretic hormone cause excessive water loss in the urine. Oxytocin causes contraction of the smooth muscle in the wall of the uterus. It also stimulates the ejection of milk from the lactating breast.
The pineal gland, also called pineal body or epiphysis cerebri, is a small cone-shaped structure that extends posteriorly from the third ventricle of the brain. The pineal gland consists of portions of neurons, neuroglial cells, and specialized secretory cells called pinealocytes. The pinealocytes synthesize the hormone melatonin and secrete it directly into the cerebrospinal fluid, which takes it into the blood. Melatonin affects reproductive development and daily physiologic cycles.
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.
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.
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.
Causes & 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.
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
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