The pituitary gland is called the master gland of the endocrine system because i
ID: 133149 • Letter: T
Question
The pituitary gland is called the master gland of the endocrine system because it releases so many different hormones and those, in turn, cause the release of many other hormones from glands further down the chain of command within the system. Pick one hormone that the pituitary gland releases and tell us about what that hormone does for us. Then research what would happen if that hormone were over-secreted and what would happen if it were under-secreted Explain how the body would react to these changes in hormone levels.Explanation / Answer
The pituitary gland, also known as the 'master endocrine gland, secretes a large number of hormones which directly or indirectly control the secretion of other endocrine glands and thus affect a large number of functions in the body.
Adrenocorticotropic [ACTH], Thyroid Stimulating Hormone [TSH], Follicle Stimulating Hormone [FSH], Luteinizing Hormone [LH], Growth Hormone [GH], Prolactin etc are just to name a few.
Let us discuss the role of Growth Hormone [GH] and the role it plays in our body.
Growth hormone[ GH ], also called Somatotropin, is secreted by the anterior lobe of the pituitary gland. It stimulates the growth of all the tissues, including the bones, of the body. Normally, about 1 to 2 mg of this hormone is secreted by the pituitary gland each day.
GH is important for normal growth in children. Its level rises progressively during childhood and peaks during puberty. This is responsible for the growth spurt seen during puberty and adolescence. Normally, after this, the concentration of GH in the blood decreases.
GH works by stimulating protein synthesis and increasing fat breakdown to provide the energy necessary for tissue growth. GH may either act directly on the tissues or it may stimulate the liver to produce and release insulin-like growth factors.
GH secretion is stimulated by Growth-Hormone Releasing Hormone [ GHRH ] and is inhibited by somatostatin.
In normal individuals, GH secretion increases in response to decreased food intake and to physiological stresses and decrease in response to food ingestion. But there are cases of abnormalities in the secretion of this hormone which might include both oversecretions or deficiency of GH in the body.
* GH deficiency results in a condition called dwarfism. This condition results in the short stature or poor physical growth of the individual. The main reason for such a condition results from damage to the hypothalamus or to the pituitary gland during fetal development. Or it may result due to a mutation in genes that regulate the synthesis and secretion of GH. In some cases, it has been found that the somatotrophs [ cells which produce GH ] are incapable of doing so or the hormone itself is structurally abnormal and has little or no growth promoting activity.
Sometimes, short stature and GH deficiency is seen in children who are living under severe emotional stress. Luckily for such children, if they are removed from the stress conditions, their endocrine function and growth rate normalises.
In some other cases, GH deficiency can be treated with injections of GH.
*If there is an excess production of GH in the body, it results in a condition called gigantism. As the name suggests, this is a condition when the body grows abnormally in height and other physical features.
Excess GH production is mostly caused due to the growth of a benign tumour [ adenoma ], of the somatotrophic cells of the pituitary gland. In some cases, a tumour in the lungs or the pancreatic 'islets of Langerhans' produces GHRH which in turn stimulates the somatotrophs to produce an excess of GH. In some rare cases, it has been found that tumour cell in tissues which do not normally synthesize GH, begin to secrete this hormone, causing abnormal growth.
* The body is directly affected by the over or under production of GH by the pituitary. If the GH is produced in excess, the body responds by overgrowth and acromegaly [ disproportionate growth of facial features or other body parts]. The side effects of such a condition are the development of diabetes mellitus, high blood pressure, arthritis, cardiovascular diseases etc. Treatment of acromegaly includes surgical removal of a pituitary tumour or radiation therapy. Certain drugs, like pegvisomant, is used to treat this condition. It works by blocking the binding of GH to its receptors and thus interfering with its action.
Less production of GH results in a poor and improper growth of the body, resulting in dwarfism. This can be corrected to some extent by injecting GH into the individuals suffering from this condition.
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