Hypothyroidism v. Hyperthyroidism
Celine Nicole Saenz
Coronado High School
February 10th, 2015
Thyroid Gland Activity
Hypothyroidism v. Hyperthyroidism Both over-activity and under activity of the thyroid gland can cause severe metabolic disturbances. Hypothyroid disorders may result from some thyroid gland defect or secondarily from inadequate TSH or TH release. Hyperthyroid disorders mar result in autoimmune diseases. Though each involve the thyroid gland, the two are very different in the effects they have on the body. By examining the thyroid and its functions, a clearer understanding can then be drawn of the importance it hold in maintaining homeostasis in the human body.
In order to maintain homeostasis, the human body relies heavily on the endocrine system to control and regulate intercellular communication through the use of chemical signaling. These signals are sent out by endocrine glands through chemicals known as hormones, which in turn travel all over the body primarily through the blood steam. Once the hormones reach their target cells—the intended recipient of the chemical signal—they bind to its receptors, producing the intended response. Each endocrine gland has a specific set of signals it can release and accept, thereby giving each one its own role in keeping the body in homeostasis. The “master gland” of the endocrine system is the hypothalamus. The hypothalamus secretes a hormone signal to stimulate either the anterior or posterior pituitary gland (the middle man between the hypothalamus and all other organs) which intern releases the requested hormone that goes on to bind with their intended target cells and these target cells then change as per requested by the hypothalamus. One of the many target cells is the thyroid gland. Located anterior to the trachea, just inferior to the larynx, the thyroid closely resembles that of a butterfly and is made up of mostly thyroid follicles. Within these follicles’ central cavity is a viscous fluid containing glycoprotein thyroglobulin called the colloid. The colloid is where the thyroid hormone is produced, a hormone widely used in the body (OpenStax, 2013, p. 715-719).
Thyroid and Homeostasis
Low blood levels of T3 and T4 stimulate hypothalamus to release thyrotropin-releasing hormone (TRH) that goes on to start the production of thyroid stimulating hormone (TSH) in the anterior pituitary. When the anterior pituitary gland releases the TSH to start the production of two types of hormones, triiodothyronine (T3) and thyroxine (T4), in the thyroid gland. The production of these hormones is dependent on the presence of iodine. Once the hormones are made they are released into the blood stream and bind to transport proteins called thyroxin-binding globulins, albumin, or other plasma proteins. While some of the T3 and T4 continue to float freely in the blood, the ones that were bound wait until blood levels of T3 and T4 are low to break off to replenish it. Summarized:
1. Low blood levels of T3 and T4 cause the hypothalamus to secrete TRH
2. The TRH signals the anterior pituitary to release TSH
3. The TSH stimulates the secretion of T3 and T4 from the thyroid.
4. Increased levels of T3 and T4 decreases the production and secretion of TSH
The hormones T3 and T4 play an important role in the body as they effects the amount of energy used by the body at rest, are required for protein synthesis, development and growth of tissue and the nervous system in utero and childhood, support adult neurological functions, influence libido, fertility and other reproductive functions, and increase the body’s sensitivity to catecholamines (OpenStax College, 2013, p. 718). In all, because the thyroid hormones regulate so many important body functions, any type of thyroid disorder can be detrimental to one’s health. Also, the hormone calcitonin, which is produced by the parafollicular cells, is released by the thyroid gland. Unlike