Hypothyroidism: Thyroid-stimulating Hormone

Hypothyroidism Hypothyroidism is a condition where the thyroid does not produce enough of the hormones that are required to maintain metabolism (Harvard School of Medicine, 2007). Introduction Hypothyroidism is not a disease itself, but is a condition that a disease state causes (Buckley & Schub, 2008). Many of the causes of hypothyroidism are related to autoimmune conditions, where the body attacks itself, rendering the thyroid useless (Raisbeck, 2009). In fact, this is the most common cause of hypothyroidism (Raisbeck, 2009). Second to autoimmune disease is overcorrection of hyperthyroidism by surgery or radiation treatment (Walker, 2009).

Thyroidectomy is the third most-prevalent cause, usually for the treatment of cancer (Walker, 2009). Diagnosis of hypothyroidism is not always easy. Patients often present with vague symptoms, such as depression, lethargy, weight gain, sensitivity to cold, and dry skin (Harvard School of Medicine, 2007). Often, patients are treated for other disease states before the thyroid disorder is discovered and treated (Buckley & Schub, 2008). Biochemistry Description Thyroid Stimulating Hormone (TSH) is a peptide hormone that is produced in the adrenal glands.

Its purpose is to cause thyroxine (T4) and triiodothyronine (T3) to be produced by the thyroid (Harvard School of Medicine, 2007). Production of TSH is caused by the production of thyrotropin-releasing hormone (TRH) in the hypothalamus (Harvard School of Medicine, 2007). When the levels of T3 and T4 are low, the hypothalamus releases TRH, which causes the adrenal glands to produce TSH, which will cause the thyroid to produce hormones (Raisbeck, 2009). The levels of T3 and T4 are high, TRH output is reduced, causing reduction in TSH production (Raisbeck, 2009).

The thyroid hormones are involved in metabolism in every cell of the body (Buckley & Schub, 2008). In addition to setting the basal metabolic rate, the hormones are involved in protein synthesis and regulating long bone growth (Buckley & Schub, 2008). Thyroid hormones also regulate protein, fat, and carbohydrate metabolism (Buckley & Schub, 2008). When the thyroid does not react to the higher TSH levels, hypothyroidism results (Buckley & Schub, 2008). As noted, the cause is usually from the body’s own antibodies attacking the thyroid (Raisbeck, 2009).

This attack renders the thyroid unable to produce thyroid in sufficient quantities to support the entire body (Buckley & Schub, 2008). In some cases, however, there can be a resistance to the actual thyroid hormones that the body has created (Fukata, Brent, & Sugawara, 2005). This becomes evident when the TSH level remains high and the T3 and T4 levels are normal or elevated, after medication is begun (Fukata, Brent, & Sugawara, 2005). Methods of Treatment Treatment of hypothyroidism is based on replacement of the thyroid hormones that the body is incapable of producing (Hennefer & Lawson, 2009).

Replacement of one or both of the thyroid hormones is done, in oral form, with a synthesized hormone (Hennefer & Lawson, 2009). Initially, the thyroid hormones were obtained from swine sources, but most production has switched to a synthetic product (Hennefer & Lawson, 2009). Hypothyroidism affects many of the body’s systems (Greco, 2001). Myxedema coma, a rare, but often fatal condition that results from extremely low levels of thyroid hormone, is prevalent in the elderly during colder weather (Greco, 2001).

Patients present to emergency departments with altered mental status, a low core body temperature, edema of the whole body, and hyponatremia (Greco, 2001). Often, as the prevalence is in the cold weather, patients are mistaken for simple hypothermia. Alas, by the time the correct diagnosis is made, the patient has succumbed to the condition (Greco, 2001). The cardiac system is at the mercy of thyroid hormone (Klein & Ojamaa, 2001). Thyroid hormone acts on cardiac muscle and vascular smooth-muscle cells, causing increased heart rate and blood pressure when there is an excess of thyroid hormone (Klein & Ojamaa, 2001).

The opposite is also true (Klein & Ojamaa, 2001). Care must be taken when using amiodarone, a common anti-dysrhythmic medication, with hypothyroid patients (Klein & Ojamaa, 2001). Amiodarone is iodine-rich and can cause the little thyroid function to end (Klein & Ojamaa, 2001). A recent meta-analysis seeking to find the risk of hypothyroid and coronary heart disease has found that there is a modest increase in risk for heart disease for patients with hypothyroidism (Ochs, et al. , 2008). This analysis reviewed ten studies, involving over 14,000 patients (Ochs, et al. 2008). The review showed that the incidence of heart disease in the hypothyroid patient was 20% higher than that in the patient with normal thyroid function (Ochs, et al. , 2008). Another rare, but significant finding in hypothyroid is Hashimoto’s encephalopathy (Huete, Sanchez-del-Rio, & French, 2007). Patients who have migraine headaches will often present to the emergency department with a headache that follows an aura, or a feeling that the headache is going to strike (Huete, Sanchez-del-Rio, & French, 2007).

In this study, the authors describe a patient who made such a presentation, but, rather than a simple migraine, was suffering from Hashimoto’s encephalopathy, a swelling and general dysfunction of the brain (Huete, Sanchez-del-Rio, & French, 2007). Conclusion Hypothyroidism is a serious medical condition and one that requires close follow-up by physicians. With affects on every cell in the body, it is important to maintain a normal, or near-normal, level of thyroid hormone. ? References Buckley, L. , & Schub, E. (2008). Hypothyroidism in adults. Retrieved November 5, 2009, from Cinahl quickLESSION. Fukata, S. , Brent, G. , & Sugawara, M. 2005, February 3). Resistance to thyroid hormone in Hashimoto’s thyroiditis. New England Journal of Medicine , 352 (5), pp. 517-518. Greco, L. (2001, December). Hypothyroid emergencies. Topics in Emergency Medicine , 23 (4), pp. 44-50. Harvard School of Medicine. (2007, September). Thyroid hormone: Slim fast, but will it last? Harvard Health Letter , 32 (11), p. 5. Hennefer, D. , & Lawson, E. (2009, September). Pharmacology – a systems approach: thyroid disease. British Journal of Healthcare Assistants , 3 (9), pp. 457-459. Huete, A. , Sanchez-del-Rio, M. , & French, O. (2007, January). Hashimoto’s encephalopathy mimicking migrane with aura.

Headache: The Journal of Head and Face Pain , 47 (1), pp. 130-131. Klein, I. , & Ojamaa, K. (2001, February 15). Mechanisms of disease. Thyroid hormone and the cardiovascular system. New England Journal of Medicine , 344 (7), pp. 501-509. Ochs, N. , Auer, R. , Bauer, D. , Nanchen, D. , Gussekloo, J. , Cornuz, J. , et al. (2008). Meta-analysis: Subclinical thyroid dysfunction and the risk for coronary heart disease and mortality. Annals of Internal Medicine , 148 (11), 832-845. Raisbeck, E. (2009). Understanding thyroid disease. Practice Nurse , 37 (1), pp. 34-36. Walker, C. (2009, January). Hypothyroidism. Nursing Standard , 23 (18), p. 58.