The Thyroid and our Metabolism (Sara S)

Function

Thyroid Gland

endocrine gland (a gland that secretes hormones)
located in front of the throat
sits low on the front of the neck (below the Adam's apple) and it is shaped like a bow tie or a butterfly
contains two lobes connected by a "bridge" called the isthmus
produces hormones that regulate breathing, heart rate, muscle strength, menstrual cycles, body temperature and the metabolism
very important in infancy and childhood for brain development
most important for growth, development, and maturation
thyroid cells are the only cells in the human body that absorb iodine- an important substance used to create hormones

Metabolism

our body's ability to break down food and convert it to energy
food fuels our bodies and different bodies burn that fuel at different rates
every cell in our bodies rely on the thyroid to manage our metabolism
if our metabolism was a car engine, the thyroid would be the gas

Hormones Produced by Thyroid Gland

The first two hormones:

produced by iodine from the foods we eat
thyroxine and tri-iodothyronine
Thyroxine is also known as T4 because it contains four iodine atoms
T4 is lipid soluble and can pass through the cell membrane
once T4 gets inside the cell, it can lose an iodine atom and become T3 (tri-iodothyronine) by the deiodinase system
In the brain, the hypothalamus and the pituitary take care of balancing the T3 and T4 levels
A normal functioning thyroid produces around 80% T4 and 20% T3n

Figure 1:

Ingram, C. (2015, February 09). Dr. Cass Ingram's Thyroid Gland Test [Online image]. Retrieved April 3, 2017, from https://cassingram.com/dr-cass-ingrams-thyroid-gland-test/

The Negative Feedback Loop

In the brain....

the hypothalamus secretes the thyroid releasing hormone (TRH) which signals the pituitary to release the thyroid stimulating hormone (TSH)
the thyroid then increases in size and secretes the thyroid hormones into circulation.

Role of T3 and T4

once T3 and T4 are released by the thyroid, they attach to proteins and travel in the bloodstream
travel to almost every cell in the body
when they reach a target cell, they detach from the carrier protein and work on the cell
T3 and T4 hormones regulate the speed at which the metabolism works

Figure 2:

Antranik. (2012, May 13). Thyroid Stimulating Hormone (Thyrotropin) [Online image]. Retrieved April 3, 2017, from http://antranik.org/thyroid-stimulating-hormone-thyrotropin/

Calcitonin- the third hormone produced by the thyroid

helps control blood calcium levels
lowers the level of calcium in the blood by preventing the continual release of calcium from the bones
released when the blood calcium levels rise above normal range

Abnormalities

Figure 3:

WebMD. (n.d.). Goiter [Online image]. Retrieved April 7, 2017, from http://www.webmd.com/women/goiter

Hypothyroidism

the body doesn't make enough of the thyroid hormones
metabolism slows down so this makes it hard to lose weight
sometimes causes weight gain
thyroid hormones can be prescribed by a doctor to normalize the thyroid hormone levels
most common cause is lack of iodine to make T3 and T4
can cause a goiter: the thyroid isn't producing enough thyroid hormones, so it keeps being simulated to produce more, leading to swelling

Figure 4:

Pinterest. (n.d.). Thyroid Memes [Online image]. Retrieved April 10, 2017, from https://www.pinterest.com/search/pins/?q=Meme&pin=417427459185132785&lp=plp

Hyperthyroidism

overactive thyroid
too many thyroid hormones are made
the body's processes speed up (rapid heart beat, nervousness, anxiety, hand sweating, etc.)
can be treated with antithyroid medications that interfere with the production of thyroid hormones
can also cause a goiter

Screening for Thyroid Function

the thyroid function can be tested by a blood test measuring the levels of TSH in the blood
overly high levels of TSH means that the pituitary has released lots of TSH but the thyroid isn't listening (it's like screaming louder for a person who can't hear very well- you are making lots of noise, but its just not getting through to the person)

Summary of the THYROID

Cherishyourhealthtv. (2013, June 18). Thyroid gland- What's the function of the thyroid? Retrieved April 3, 2017, from https://www.youtube.com/watch?v=xKQa-MbZUPY&t=5s

References

Andrews, R. (2015, November 12). All About The Thyroid. Retrieved April 03, 2017, from http://www.precisionnutrition.com/all-about-thyroid

Antranik. (2012, May 13). Thyroid Stimulating Hormone (Thyrotropin) [Online image]. Retrieved April 3, 2017, from http://antranik.org/thyroid-stimulating-hormone-thyrotropin/

Brady, B. (n.d.). Thyroid Gland, How it Functions, Symptoms of Hyperthyroidism and Hypothyroidism. Retrieved April 03, 2017, from https://www.endocrineweb.com/conditions/thyroid-nodules/thyroid-gland-controls-bodys-metabolism-how-it-works-symptoms-hyperthyroi

Cherishyourhealthtv. (2013, June 18). The thyroid gland- What's the function of the thyroid? Retrieved April 03, 2017, from https://www.youtube.com/watch?v=xKQa-MbZUPY

Ingram, C. (2015, February 09). Dr. Cass Ingram's Thyroid Gland Test [Online image]. Retrieved April 3, 2017, from https://cassingram.com/dr-cass-ingrams-thyroid-gland-test/

Jaques, J. (n.d.). The Role of Your Thyroid in Metabolism and Weight Control. Retrieved April 03, 2017, from http://www.obesityaction.org/educational-resources/resource-articles-2/general-articles/the-role-of-your-thyroid-in-metabolism-and-weight-control

MacGill, M. (2015, September 24). Goiter: Causes, Symptoms and Treatments. Retrieved April 06, 2017, from http://www.medicalnewstoday.com/articles/167559.php

Ministry Health Care. (n.d.). Your thyroid is your metabolic control center. Retrieved April 03, 2017, from http://ministryhealth.org/HC/Home/Spring2010/Yourthyroidisyourmetaboliccontrolcenter.nws

Pinterest. (n.d.). Thyroid Memes [Online image]. Retrieved April 10, 2017, from https://www.pinterest.com/search/pins/?q=Meme&pin=417427459185132785&lp=plp

WebMD. (n.d.). Goiter [Online image]. Retrieved April 3, 2017, from http://www.webmd.com/women/goiter

Thyroid Cancer

more common in women and those over 30
the first sign is often a thyroid nodule (a lump), however, fewer than 1% of thyroid nodules are malignant (cancerous)
4 different types of thyroid cancer
the most common type of thyroid cancer is very curable
Treatment: the thyroid is normally taken out, poisonous iodine is put into the body to kill the remaining thyroid cells (no other cells will be harmed because the thyroid cells are the only ones to absorb iodine), and thyroid hormone pills will need to be taken

Goiter

normally caused by a lack of iodine in the diet
the body isn't able to make T4
the negative feedback loop fails
thyroid is constantly stimulated by TSH from the pituitary gland (remember that when TSH is released, it causes the thyroid gland to enlarge to secrete T3 and T4)
the thyroid becomes overstimulated and it keeps growing larger eventually causing the thyroid to swell to a very large size

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