Posted by Kelsey Bishop
Biol 112
Don Larson
STEAM Project
Hypothyroidism
My art project is on Hypothyroidism and the objectives I am covering are “describe how hormones interact with production and control of other hormones” and “ provide examples of positive and negative feedback”. In my project I have drawn a flow chart of the Hypothalamus-Pituitary-Thyroid complex and in it I have noted what hormones are involved and which hormones are high and low in a patient with hypothyroidism.
The thyroid is a small gland located at the front of the neck under the skin and in front of the trachea. The thyroid produces and releases four hormones: Triiodothyronine (T3), Thyroxine (T4), Reverse triiodothyronine (RT3), and Calcitonin. The main function of the thyroid is to maintain the body’s metabolic rate but these hormones affect a vast array of things within the human body including heart rate, breathing, digestion, body temperature, brain development, mental activity, skin and bone maintenance, and fertility. The thyroid gland needs iodine in order to produce all of these hormones.
A negative feedback is when the increased production and release of a hormone causes a hormone up the chain to decrease thus decreasing the release of the initial hormone. Positive feedback is when the production and release of a hormone increases the release of another hormone up the chain thus increasing the release of the initial hormone. In the case of the thyroid gland, Thyrotropin-Releasing Hormone (TRH) from the Hypothalamus stimulates the release of Thyroid-Stimulating Hormone (TSH) from the Anterior Pituitary Gland which stimulates the release of T3 and T4 from the Thyroid. As more T3 and T4 are released, the blood serum levels of each increase and inhibits the release of TSH and TRH (Feldt-Rasmussen et al., 2021).
Hypothyroidism is a condition of thyroid hormone deficiency. Due to the absence of symptom specificity, hypothyroidism is defined on the biochemical level (Chaker et al., 2017). Levels of TSH in clinical hypothyroidism are above the reference range while levels of T4 are below the reference range. In subclinical hypothyroidism, TSH is also above the reference range but T4 is normal (Chaker et al., 2017). There are different classifications of hypothyroidism. Primary is due to a deficiency in thyroid hormone, secondary is due to a deficiency in thyroid-stimulating hormone, and tertiary is due to a deficiency in thyrotropin-releasing hormone. Peripheral hypothyroidism is also known as extra-thyroidal hypothyroidism (Chaker et al., 2017). Like previously mentioned, symptoms of hypothyroidism are not specific and range depending on the patient. However, commonly reported symptoms include fatigue, weight gain, trouble tolerating the cold, joint and muscle pain, dry skin, dry or thinning hair, heavy or irregular menstrual periods or fertility problems, slowed heart rate, and depression (Hypothyroidism (underactive thyroid) – NIDDK).
The standard treatment for patients with hypothyroidism is thyroid hormone replacement with levothyroxine. Combined levothyroxine and liothyronine therapy have been done but it has not been found to have better results than only levothyroxine (Chaker et al., 2017). A thyroidectomy is also a treatment for certain thyroid diseases as a person can live a normal life without a thyroid, however they will need to take hormone replacement medication for the rest of their life (Cleveland Clinic).
Professional, C. C. medical. (n.d.). Thyroid: What it is, Function & Problems. Cleveland Clinic. https://my.clevelandclinic.org/health/body/23188-thyroid
U.S. Department of Health and Human Services. (n.d.). Hypothyroidism (underactive thyroid) – NIDDK. National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/endocrine-diseases/hypothyroidism
Feldt-Rasmussen, U., Effraimidis, G., & Klose, M. (2021, January 18). The hypothalamus-pituitary-thyroid (HPT)-axis and its role in physiology and pathophysiology of other hypothalamus-pituitary functions. Science Direct. https://www.sciencedirect.com/science/article/pii/S0303720721000174?via%3Dihub
Chaker, L., Bianco, A. C., Jonklaas, J., & Peeters, R. P. (2017). Hypothyroidism. The Lancet, 390(10101), 1550–1562. https://doi.org/10.1016/s0140-6736(17)30703-1
Lymphadenitis Abstract by Kelsey Bishop for Savannah Cowley
https://humanap.community.uaf.edu/2024/04/18/lymphadenitis/
The objectives covered in this project were “identify the key structures of the lymphatic system” and “relate how the lymphatic system can indicate disease”. The lymphatic system is a network of vessels that picks up leaked fluids as they are weaved in between capillary beds. The main function of the lymphatic system is to filter the fluid, also called lymph, and return it to the circulatory system. This helps maintain a balance of fluids in the body. Another primary function of the lymphatic system is immune-centered as white blood cells called lymphocytes are produced within the system. In addition to the lymphatic vessels, the lymphatic system consists of the spleen, thymus, lymph nodes, and tonsils. Each organ has its own function within the immune system. The lymph nodes are the most important and function as lymph filters to remove bacteria and foreign cells. When the lymph nodes are overwhelmed, they become irritated or infected in a condition called Lymphadenitis. Symptoms include swollen lymph nodes, tenderness in the surrounding area, redness around the infected sites, and excess fluid build up. In simple cases, lymphadenitis is typically untreated and heals over time. In more severe cases, antibiotics and other medications may be prescribed.
From Kelsey’s research, I have learned how important the thyroid’s hormones are. The thyroid releases four hormones: T3, T4, RT3, and calcitonin. These hormones work together to control bodily functions such as heart rate, metabolism, digestion, breathing, temperature, and fertility (Bishop, K., Hypothyroidism, para. 2). Hypothyroidism is defined as a thyroid hormone deficiency. It is hard to diagnose because the symptoms produced are not specific to this disease process alone. A hormone level test must be performed to accurately diagnose hypothyroidism. This is because hypothyroidism causes TSH levels to be extraordinarily high, while T4 and T3 levels remain the same. It has been found that when TSH is brought down to a normal level, T3 and T4 are actually very low. This means that TSH is so high because it is overcompensating to make T3 and T4 hormones reach a normal level (Bishop, K., Hypothyroidism, para. 4). In doing so, a positive feedback loop is created rather than the negative feedback loop that should be present as shown in Kelsey’s chart. The production of inadequate T3 and T4 stimulates the production of more TSH, which produces more T3 and T4, and therefore more TSH, meaning that the cycle builds upon itself. From Kelsey’s chart, we can see how the production of T3 and T4 are supposed to shut off the production of TSH, and the complications that might occur if that doesn’t happen. Typically, the treatment for hypothyroidism is hormone therapy and the potential removal of the thyroid itself (Bishop, K., Hypothyroidism, para. 5).