Teaching Notes
“My Brother Calls Me ‘Bug Eyes’”: A Case Study on the Endocrine System
Introduction
This case study tells the story of Krista, a college student who is experiencing a series of seemingly unrelated symptoms. She receives a diagnosis of Graves’ disease, an autoimmune disorder that causes the thyroid gland to become hyperactive. Students explore the general actions and regulation of the thyroid hormones and how hyperactivity of the thyroid leads to Krista’s specific symptoms.
Graves’ disease is the most common form of hyperthyroidism, affecting more women than men. Common signs and symptoms include unexplained weight loss, excessive perspiration, elevated pulse, diarrhea, and a feeling of nervousness. Auto-antibodies bind to and activate the TSH receptors in the thyroid gland, causing the thyroid to secrete excessive amounts of thyroxine and triiodothyronine (collectively referred to as thyroid hormone). Levels of TSH are correspondingly low but have no effect due to the continued presence of the auto-antibodies.
Objectives
Upon completion of this case, students will be able to:
· List the thyroid hormones and describe their actions.
· Describe the symptoms associated with hyperthyroidism.
· Understand the roles of thyroid-stimulating hormone (TSH) and thyrotropin releasing hormone (TRH) in regulation of thyroid hormone secretion.
Prerequisites
Students should:
· Know the basic anatomy and function of the hypothalamus, pituitary gland, and thyroid gland.
· Understand the role of negative feedback in the regulation of hormone secretion.
· Understand directional terms such as anterior and posterior.
Classroom management
This case study may be used as an in-class assignment or as a homework assignment following presentation of material on the pituitary and thyroid glands (including the hormones secreted, their general actions, and the role of negative feedback). Alternatively, the case may be used to teach the topic of the thyroid gland and its regulation. If used in this way, the instructor may wish to group the questions as follows:
· The thyroid gland and its hormones: short answer questions 1-2; multiple choice questions 1-3.
· Regulation by the pituitary and hypothalamus: short answer questions 3–5 and 8; multiple choice questions 4–6.
· The etiology of Graves’ disease: short answer questions 6–7.
The learning objectives are straightforward, but care should be taken to address several areas of potential confusion. The similarity of the abbreviations TRH, TSH and TH (for thyroid hormone) causes students to easily mistake one for another. Students also often mistakenly think TSH is produced by the thyroid, so there are several questions in the case that address this point. Lastly, students may or may not be familiar with the concept of autoimmunity, so a brief description may need to be included.
Graves’ disease is the most common cause of hyperthyroidism, but other causes exist (nodules, thyroiditis, pregnancy, etc.). Multiple choice question 5 introduces the rare situation of a pituitary tumor, which allows the instructor to reinforce the relationship between TSH and thyroid hormone.
As with any medical condition, signs and symptoms will vary with the individual. In this case study, Krista experiences most of the typical signs and symptoms associated with Graves’ disease in order to introduce students to them and reinforce the actions of the thyroid hormones. It would be beneficial during class discussion to note that some patients only experience one or a few of the common signs and symptoms, and exophthalmos is only present in some cases.
Additional resources
Brent G.A., 2008. Clinical practice: Graves’ disease. The New England Journal of Medicine 358: 2594-2605.
“Graves’ disease.” Mayo Foundation for Medical Education and Research. http://www.mayoclinic.com/health/Graves’-disease/DS00181. Accessed August 26, 2009.
“Graves' disease.” U.S. Department of Health and Human Services. http://www.endocrine.niddk.nih.gov/pubs/Graves’/Graves’.pdf. Accessed August 28, 2009.
Hershman, J.M., ed. 2009. “Hyperthyroidism.” In The Merck Manuals Online.
http://www.merck.com/mmpe/sec12/ch152/ch152e.html#sec12-ch152-ch152e-242. Accessed November 6, 2009.
“Hyperthyroidism.” American Association of Clinical Endocrinologists. http://www.aace.com/pub/thyroidbrochures/pdfs/Hyperthyroidism.pdf. Accessed August
28, 2009.
Kung A.W.C., 2007. Neuromuscular complications of thyrotoxicosis. Clinical Endocrinology 67: 645–650.
Norman J., “Your thyroid gland.” Vertical Health.
http://www.endocrineweb.com/thyroid.html. Accessed August 26, 2009.