The Thyroid
The Thyroid
The Thyroid Gland
The thyroid, located on the inside of the neck (as shown in image), is one of the largest glands of the endocrine system. The thyroid is made up of two lobes bound by the isthmus and is located just below the larynx.[1]
What Does the Thyroid Gland do?
As all other glands of the endocrine system, the thyroid produces and releases hormones. Hormones produced by the thyroid give the body energy, regulate body temperature, and promote proper organ function[2] by controlling “how quickly the body burns energy, makes proteins, and how sensitive the body should be to other hormones.”[3] The biochemistry behind how this regulation occurs is very complex.
Which Hormones Does the Thyroid Produce?
Thyroxine (3,5,3′,5′-tetraiodothyronine,[4] or T4) is the major hormone secreted by the thyroid. The other hormone produced by the thyroid is the Triiodothyronine hormone (T3).[5] A healthy thyroid can produce up to four times as much T4 than T3 (T3 has larger influence on target cells than T/4). These are made by thyroid cells commonly known as follicular cells or principal cells.[6]
How Does the Thyroid Create T3 and T4?
Looking at their structure, you can see that T3
and T4
contain a lot of Iodine (I). The two structures are very similar. In fact, almost identical. The only difference is that T4 has one extra Iodine group than T3. The thyroid takes iodine found in the foods you eat and uses them to create T3 and T4 by combining it with tyrosine[1] (an essential amino acid).
Triiodothyronine and thyroxine are then released directly into the blood where they will be delivered to all every cell in the body. Every cell in the body depends on these two thyroid hormones for regulation of their metabolism.
Thyroid-Stimulating Hormone
It is important to note that the thyroid, and thus T3 and T4 production, is controlled by the thyroid-stimulating hormone (TSH) secreted by thyrotrope cells in the anterior pituitary gland.[7]
References:
[1] EndocrineWeb. “How Your Thyroid Works.”
Available at: http://www.endocrineweb.com/thyfunction.html
Accessed August 04, 2009.
[2] LearningInfo.org. “The Function of the Thyroid Gland”.
Available at: http://health.learninginfo.org/function-thyroid-gland.htm
Accessed August 04, 2009.
[3] Wikipedia. “Thyroid”.
Available at: http://en.wikipedia.org/wiki/Thyroid
Accessed August 04, 2009.
[4] Wikipedia. “Thyroxine”.
Available at: http://en.wikipedia.org/wiki/Thyroxine
Accessed August 04, 2009.
[5] Wikipedia. “Triiodothyronine”.
Available at: http://en.wikipedia.org/wiki/Triiodothyronine
Accessed August 04, 2009.
[6] Wikipedia. “Thyroid Epithelial Cell”.
Available at: http://en.wikipedia.org/wiki/Thyroid_epithelial_cell
Accessed August 04, 2009.
[6] Wikipedia. “Thyroid-stimulating Hormone”.
Available at: http://en.wikipedia.org/wiki/Thyroid-stimulating_hormone
Accessed August 04, 2009.
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