Karina Martin
Mr. Quick
A Block - 2/24/14
Hello, today I am going to talk about the endocrine system. More specifically, I am going to talk about the T3 and T4 hormones located in the thyroid gland. TSH, otherwise known as thyroid-stimulating hormone, is released from the pituitary, an endocrine gland that sits just beneath the base of the brain. From the pituitary, TSH goes into the bloodstream and travels to the thyroid gland. Here, TSH causes cells within the thyroid to produce more T3 and T4 hormones.
This whole process of producing T3 and T4 hormones starts in the portal capillaries where thyrotropin-releasing hormone or TRH is secreted and then sent to the anterior pituitary, the endocrine gland I mentioned before located beneath the brain. There, TRH stimulates thyrotropes (hormones produced by the anterior lobe of the pituitary) to synthesize and release TSH. You already know what happens next. The TSH makes its way to the thyroid gland and then (TADA!) we have T3 and T4 hormones.
T3 and T4 hormones have a negative feedback loop that regulates the secretion of TSH. If TSH is not secreted, thyroid function becomes depressed and the thyroid gland wastes away. Control of TSH stimulates the thyroid gland and increases circulating levels of thyroid hormones. In other words, no TSH equals no thyroid gland which equals short life which equals BAD! You see, the thyroid plays a very important role in a human’s metabolism. Hormones T3 and T4 have an effect on every cell in the body. They control the rate in which the cells in your body use energy and oxygen. Because thyroid hormones play such an important role in the function of the brain, a deficiency of thyroid hormone can cause depression, memory problems, and even psychosis. Thyroid hormones are also important when it comes to human growth and development; therefore, hormone deficiency can also cause severe mental retardation and serious growth delays.
Now, remember when I talked about TSH? Well, when in the process of making its way from the pituitary to the thyroid gland, TSH is given instructions by a gene receptor called TSHR. This receptor extends itself throughout the membrane of follicular cells in the thyroid gland. It serves as a customized binding site for the TSH hormone. TSH attaches itself to the extracellular portion of the receptor, activating a series of reactions that control the development of the thyroid gland and its functions.
Thyroid hormones are poorly soluble in water. They are lipid soluble, however, and diffuse into the cell, where they, as I mentioned before, attach themselves to receptors, migrate to the nucleus, and activate specific target sequences of DNA. On the other hand, water soluble hormones use their effects through an intracellular second messenger that is activated when a hormone attaches itself to a membrane receptor.
The thyroid gland is an important part of your body. As I mentioned before, it is very difficult to survive without one. Some people don’t have thyroid glands however. And if you are, don’t freak out! While the hormones a thyroid produce are essential to life, people can live without a thyroid gland as long as the hormones are replaced. A thyroid hormone can be replaced with a synthetic one. Interesting, right? Well, that’s all I have to say about thyroid hormones. Thanks for listening!
Here is the link to my podcast: https://drive.google.com/file/d/0BwtzLZZCgHBqekludWlzWndFYTQ/edit?usp=sharing
Works Cited
- http://voices.yahoo.com/can-live-without-thyroid-gland-6993008.html?cat=5
- http://classes.midlandstech.edu/carterp/Courses/bio211/chap16/chap16.htm
- http://ghr.nlm.nih.gov/gene/TSHR
- http://mcb.berkeley.edu/courses/mcb135e/thyroid.html
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