I will be covering the objective on how the nervous system and endocrine system interact with each other with respect to the thyroid gland and the condition of hypothyroidism.

To understand the condition of hypothyroidism, we must first look at how the thyroid gland works with both the endocrine and nervous system. The thyroid gland has numerous functions in our body and secretes important hormones thyroxine (T4) and triiodothyronine (T3) which are controlled and regulated by the thyroid-stimulating hormone (TSH) which is secreted by the anterior pituitary gland. T3 is made from T4 through deiodination. (Rinaldi et al., 2014) The secretion and regulation of thyroid hormone T4 and T3 is controlled by a feedback loop system that begins in the hypothalamus (which has neural and endocrine functions) when it releases thyroid-releasing hormone (TRH) which stimulates the pituitary gland to produce thyroid-stimulating hormone (TSH) which will trigger the thyroid to produce T4 and T3 (Schroeder, A. C., & Privalsky, M. L., 2014). These hormones affect and control our body’s metabolism rate and can slow down or speed your heart up, control your body temperature, affect brain development, control the way your muscles contract, and manage the skin and bone by changing the rate in which your body replaces dying cells (Professional, n.d.) Hypothyroidism is a condition that occurs when the thyroid is not producing enough of the thyroid hormone to maintain homeostasis. (Society, 2022) it typically occurs due to a dysfunction of the thyroid itself, but in some cases it can be caused by defects along the hypothalamic-pituitary axis. It can also be caused by certain medications. Subclinical hypothyroidism is a mild form of the condition whereas overt hypothyroidism is defined as an increase of TSH and a decrease of T4 and is much more intense in its symptoms. Signs and symptoms of this condition are as follows:

  • Eyebrow and hair thinning
  • Fatigue
  • Skin coarsening 
  • Weight gain
  • Tendon relaxation phase slowing 
  • Cold intolerance
  • Facial/periorbital edema 
  • Mental slowing
  • Macroglossia
  • Muscle weakness
  • Bradycardia 
  • Reduced exercise capacity
  • Pericardial effusion 
  • Constipation
  • Pleural effusion 
  • Xeroderma
  • Rhabdomyolysis 
  • Depression
  • Menstrual irregularities  (Drake, Matthew T., 2018) 

This condition, when in the form of primary or overt hypothyroidism, left  untreated, can have serious health effects and lead to death. Subclinical hypothyroidism is a sign of early thyroid failure.The prevalence of overt hypothyroidism in the general population is between 3–7% in the USA. The environment also plays a part in the prevalence of this condition. A low or a severely high intake of iodine (which is an essential component for the thyroid hormone) in a population can increase the risk of getting hypothyroidism. It is also more prevalent in women than men and increases with age.  (Chaker, L., Bianco, A. C., Jonklaas, J., & Peeters, R. P., 2017) The most common cause would be the autoimmune disease Hashimotos, which makes antibodies in the immune system attack immune cells (Hypothyroidism (Underactive Thyroid) – Symptoms and Causes – Mayo Clinic, n.d.) . The most common treatment for this condition is levothyroxine, which is a hormone replacement for thyroxine (T4). This allows the body the sufficient amount of thyroid hormone it needs to perform normal functions of the thyroid gland and typically eliminates the symptoms of hypothyroidism. (Hypothyroidism (underactive thyroid) – Diagnosis and treatment – Mayo Clinic., 2022) In my art project, I demonstrate what hypothyroidism does to the thyroid gland and depict how the thyroid gland is regulated through a negative feedback loop controlled by the hypothalamus-pituitary-thyriod axis.  


Rinaldi, S., Plummer, M., Biessy, C., Tsilidis, K. K., Østergaard, J. N., Overvad, K., Tjønneland, A., Halkjær, J., Boutron‐Ruault, M., Clavel‐Chapelon, F., Dossus, L., Kaaks, R., Lukanova, A., Boeing, H., Trichopoulou, A., Λάγιου, Π., Trichopoulos, D., Palli, D., Agnoli, C., . . . Franceschi, S. (2014). Thyroid-Stimulating hormone, thyroglobulin, and thyroid hormones and risk of differentiated thyroid carcinoma: the EPIC study. JNCI: Journal of the National Cancer Institute, 106(6). https://doi.org/10.1093/jnci/dju097

Yoo, W. S., & Chung, H. K. (2021). Subclinical Hypothyroidism: Prevalence, Health Impact, and Treatment Landscape. Endocrinology and metabolism (Seoul, Korea), 36(3), 500–513. https://doi.org/10.3803/EnM.2021.1066

Society, E. (2022, January 24). Thyroid and parathyroid hormones. Endocrine Society. https://www.endocrine.org/patient-engagement/endocrine-library/hormones-and-endocrine-function/thyroid-and-parathyroid-hormones

Professional, C. C. M. (n.d.). (2022) Thyroid hormone. Cleveland Clinic. https://my.clevelandclinic.org/health/articles/22391-thyroid-hormone

Schroeder, A. C., & Privalsky, M. L. (2014). Thyroid hormones, t3 and t4, in the brain. Frontiers in endocrinology, 5, 40. https://doi.org/10.3389/fendo.2014.00040

Drake, Matthew T. (2018) Hypothyroidism in Clinical Practice. Mayo Clinic Proceedings, Volume 93, Issue 9, 1169 – 1172 (https://doi.org/10.1016/j.mayocp.2018.07.015)

Hypothyroidism (underactive thyroid) – symptoms and causes – Mayo Clinic. (n.d.). Mayo Clinic.




Chaker, L., Bianco, A. C., Jonklaas, J., & Peeters, R. P. (2017). Hypothyroidism. Lancet (London, England), 390(10101), 1550–1562. https://doi.org/10.1016/S0140-6736(17)30703-1

Hypothyroidism (underactive thyroid) – Diagnosis and treatment – Mayo Clinic. (2022, December 10).https://www.mayoclinic.org/diseases-conditions/hypothyroidism/diagnosis-treatment/drc-20350289

One Comment

  1. Chloe’s project demonstrates the objective of connecting the nervous system and endocrine system, and how they interact with each other within the condition of hypothyroidism.
    The thyroid has many functions to maintain homeostasis. It all begins with a feedback loop at that hypothalamus that releases thyroid releasing hormone (TRH) to the pituitary gland. In the pituitary gland thyroid stimulating hormone (TSH) is sent to the thyroid to regulate and control how much thyroxine(T4) and triiodothyronine (T3) is being secreted. T4 and T3 are produced within the thyroid gland and secreted out to our tissues. These hormones help metabolize our body by our brain growth, heart rate, muscle movement, generate new cells to skin and bone in replacement of the dying cells.
    Hypothyroidism is a condition that takes place in the thyroid or in some case in the hypothalamic pituitary axis. This affects and declines the production of hormones that maintain homeostasis. This dysfunction may be associated with certain medications, environment, and high consumption of iodine. There are studies that show this condition being more common in women than men as they increase in age. A few signs and symptoms for hypothyroidism are bradycardia, tachycardia, fatigue, muscle weakness, slow cognitive, hair thinning, increase in weight, and depression. Treatments for these conditions are hormone replacement called levothyroxine for T4. Levothyroxine allows the body to acquire a great amount of thyroid hormone to function normally.
    Chloe’s abstract showed this process by guiding my eyes through the process in which this occurs. This gives me a simple yet clear visual understanding of how it all connects and works.

    Alexandra Rivera Domagalski

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