Use of Levothyroxine in Hypothyroidism Treatment

Levothyroxine1

Use of Levothyroxine in Hypothyroidism Treatment

Dacy Gaston

South University

Use of Levothyroxine inHypothyroidism Treatment

The American Thyroid Association (2014) define hypothyroidism as the failure of the thyroid gland to produce sufficient thyroid hormone to meet the metabolic demands of the body. According to Hall (2010) there are “two types of hypothyroidism: primary and secondary. Primary hypothyroidismis a result of autoimmune destruction of the thyroid gland and accounts for over 95% of adult cases of thyroid disease. Secondary hypothyroidism is when the pituitary or the hypothalamic gland fail” (p. 381). Replacement of the deficient hormone thyroxine-4 (T4) is the gold standard in treatingprimary hypothyroidism. Levothyroxine (Synthroid); which is a synthetic version of T4,is the drug of choice in treating primary hypothyroidism (ATA, 2014). This paper will discuss

1. Hypothyroidism and its pathophysiology.
2. Levothyroxine in treatinghypothyroidism.
3. Protocol for diagnosing and treating primary hypothyroidism.
4. Diagnostic and follow up considerations.

Understanding the symptoms and management of hypothyroidism is extremely important for the well-being of the patient. Hypothyroidism is a lifelong disease that must be managed properly and assessed often. It is essential to ensure patient education and clinical management with follow up, to lead to a successful clinical outcome.

Hypothyroidism and its Pathophysiology

The hypothalamus stimulates the secretion of thyrotropin-stimulating hormone (TSH) from the anterior pituitary which stimulates the synthesis and secretion of the thyroid hormones, tri-iodothyronine (T3) and thyroxine (T4), which are then secreted into systemic circulation (ATA, 2014). T4 is produced only from the thyroid, whereas T3 is formed from the deiodination of T4 in the extrathyroidal tissues. T3 deficiency is responsible for the clinical and biochemical manifestations of hypothyroidism (Kostoglou-Athanassiou & Ntalles, 2010). Primary hypothyroidism, according to Carson (2009), occurs when there is an autoimmune, surgical or congenital destruction of the gland which leads to insufficient levels of T4 which leads to high TSH levels in the body. Secondary hypothyroidism occurs when there is pituitary or hypothalamic failure which leads to decreased TSH levels in the body. Both primary and secondary hypothyroidism have similar symptoms. Gaitonde, Rowley & Sweeney (2012) explains that“hypothyroidism hascommon physical symptoms such as depression, weight gain, dry hair, dry skin and fatigue; andclinical signs my include bradycardia, cognitive impairment, hypothermia and goiter” (p. 246). Diagnosis of hypothyroidism should be done by thyroid function tests in conjunction with the patient’s clinical symptoms (Hall, 2010). To help distinguish between primary and secondary, TSH levels are the first line of labs to be drawn in a patient suspected to have hypothyroidism (Mulryan, 2010). Normal levels of TSH are between 0.4-4.0 mU/l. When those levels are on the upper limit, hypothyroidism is suspected and free serum T4 can be drawn to conclude hypothyroidism (Kostoglou-Athanassiou & Ntalles, 2010). Treatment of choice after objective and subjective evaluationby the primary care provider begins with the administration of Levothyroxine.

Levothyroxine in Treating Primary Hypothyroidism

According to Chakera, Pearce & Vaidya (2011) Levothyroxine is the treatment of choice for hypothyroidism. Levothyroxine is a synthetic form of T4 that allows easily daily dosing because of its 7day half-life and is safe and effective when initiating dosing. The ATA (2014) states that “the guidelines for treating hypothyroidism maintain that that levothyroxine should remain the standard of care for treating hypothyroidism. We found no consistently strong evidence for the superiority of alternative preparations (e.g.levothyroxine-liothyronine combination therapy, or thyroid extract therapy, or others) over monotherapy with levothyroxine, in improving health outcomes” (p. 2). Some questions have arisen about generic versus brand name Levothyroxine. In 2004 the Food and Drug Administration approved the substitution of generic levothyroxine for brand name levothyroxine, however, the American Association of Clinical Endocrinologists, the Endocrine Society, and the American Thyroid Association all disagreed with the FDA and concluded that generic preparations were not bioequivalent to brand name Levothyroxine (Gaitonde, Rowley & Sweeney, 2012). According to Hennessey (2013) the boiequavelance of brand and generic T4 products are the same, therefore concluding that the more important aspect of treatment is the proper replacement of T4 to the body system. This can be confusing for many patients who are trying to decide on the best economical approach to hypothyroid treatment. Evidenced based practice guidelines that the ATA (2014) recommends is that if a patient is going to take generic levothyroxine then they should undergo strict repeat TSH and free T4 testing every six weeks to ensure normal range.

Levothyroxine initiation adult dosage is around 1.6 micrograms/kilograms/day and depends on various factors such as weight, age, the presence of coronary artery disease and cardiac arrhythmias (Kostoglou-Athanassiou & Ntalles, 2010). According to Chakera, Pearce & Vaidya (2011) when “initiating levothyroxine therapy, serum TSH should be measured to monitor for adequate replacement. TSH can take up to four months to normalize and it is recommended that the TSH levels be measured every 6-8 weeks after initiation or if a change in dosing is performed” (p. 3). Carson (2009) states that Levothyroxine is only partially absorbed after ingestion of food and tablets should be taken in the morning on an empty stomach. Patient adherence and education is vital to the successful treatment regimen and must be understood by the patient at onset of treatment.

According to Gaitonde, Rowley & Sweeney (2012), “there are six special populations in which to observe special consideration when administering Levothyroxine; older patients, patients with ischemic heart disease, pregnant patients, patients with persistent symptoms, patients with subclinical hypothyroidism; and patients suspected of having myxedema coma” (p. 255). In older patients and patients with ischemic heart disease, thyroid hormone increases heart rate and contractility, therefore increasing myocardial oxygen demand. These patients should be started on a lower dose of Levothyroxine to ensure safety. Pregnant patients require extra dosages of thyroid replacement because of the increase in thyroid hormone during pregnancy. Patients with persistent symptoms despite having a normal TSH level should be reevaluated for anemia, b12 deficiency, iron deficiency, anxiety, depression and viral infection. Subclinical hypothyroidism is defined by a normal free T4 level and elevated TSH level, and the association to overt hypothyroidism should be more carefully investigated. Myxedema coma can manifest itself as a severe case of hypothyroidism and is a medical emergency. Patients should be managed in an intensive care unit where they can be properly treated (Chakera, Pearce & Vaidya, 2012).

Levothyroxine is pregnancy class A, and is contraindicated in patients with untreated subclinical or overt thyrotoxicosis of any etiology and in patients with myocardial infarction. It is contraindicated in patients with uncorrected adrenal insufficiency because of the risk of the thyroid hormones that may precipitate an acute adrenal crisis (Synthroid.com, 2014).

Protocol for Diagnosing and Treating Hypothyroidism

When diagnosing hypothyroidism; symptoms, along with lab results, are measured together to conclude hypothyroidism. Common symptoms of hypothyroidism include constipation, depression, dry skin, fatigue, thinning hair, weakness, and weight gain. Clinical signs of hypothyroidism include bradycardia, cognitive impairment, edema, and goiter. Laboratory indications of hypothyroidism is based upon serum TSH and free T4 levels (see Figure 1 & 2). Evidenced based treatment guidelines recommended by the AACE (2012) and the ATA (2014) state that only Levothyroxine (T4) should be used when treating hypothyroidism, and is the standard of care after diagnosis.

Figure 1. Algorithm for evaluating suspected hypothyroidism from “Hypothyroidism: an Update,” by Gaitonde, D., Rowley, K., & Sweeney, L, 2012, American Family Physician, 86(3), 244-251. Adapted without permission.

Figure 2. Algorithm for treatment of hypothyroidism with Levothyroxine from “Hypothyroidism: an Update,” by Gaitonde, D., Rowley, K., & Sweeney, L, 2012, American Family Physician, 86(3), 244-251. Adapted without permission.

Diagnostic and Follow up Considerations

Hypothyroidism is not always the most obvious diagnosis when examining a patient. Many different diseases and disorders mimic hypothyroidism such as fibromyalgia, chronic fatigue syndrome, iodine deficiency, metabolic deficiency and viral illnesses (ATA, 2014). Shames (2012) states that “1 in 12 Americans have some degree of thyroid abnormality, people may think they just have an overweight problem when in fact they have a thyroid problem” (p. 8). He further states that “women especially can have several symptoms throughout their life such as difficulty getting pregnant, recurring miscarriages, and severe menopausal symptoms; all of which are related to thyroid function” (p. 9). Recognizing the symptoms and doing a comprehensive history and physical can direct the healthcare professional in a correct diagnosis.

Once hypothyroidism is diagnosed and Levothyroxine is started there are alternative therapies that are available but not recommended by the American Thyroid Association and the American Association of Clinical Endocrinologists. Garber et al. (2014) states that “patients have the option to take combination therapy such as Levothyroxine (T4) and Cytomel; which is the synthetic version of T3; while others can opt out for Armour which is derived from the dried powdered thyroid glands of pigs… however using anything but T4 to treat thyroid disease is controversial” (p. 6).

The most important aspect for the primary care provider to stress to the patient is strict adherence to treatment regimen (Chakera, Pearce & Vaidya, 2011). After diagnosis, lifelong treatment will be required and proper patient and family education needs to be understood. Carson (2009) explains that patients should be aware of the gradual improvement of symptoms that can take up to six months to achieve; and furthermore; patients will be advised that they will need to take T4 replacement therapy for life with repeat blood tests to evaluate treatment success. Self-management and education for the hypothyroid patient can improve adherence and lead to a successful euthyroid state for this patient population.

References:

American Thyroid Association. (2014). What is Hypothyroidism? Retrieved from

American Association of Clinical Endocrinologists. (2012). Clinical Practice Guidelines for Hypothyroidism in Adults. Retrieved from

Carson, M. (2009). Assessment and management of patients with hypothyroidism. Nursing Standard, 23(18), 48-56.

Chakera, A., Pearce, S., Vaidya, B. (2011). Treatment for primary hypothyroidism: current approaches and future possibilities. Drug Design, Development and Therapy, 6, 1-11.

Gaitonde, D., Rowley, K., Sweeney, L. (2012). Hypothyroidism: an update. American Family Physician, 86(3), 244-251.

Garber, J., Cobin, R., Gharib, H., Hennessey, J., Klein, I., Mechanick, J., Pessah-Pollack, R., Singer, P., Woeber, K. (2012). Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocrine Practice, 18(6), 692-702.

Hall, S. (2010). Prescribing in thyroid disease. Nurse Prescribing, 8(8), 382-387.

Hennessey, J. (2013). Generic vs name brand L-Thyroxine products: interchangeable or still no? Journal of Clinical Endocrinology and Metabolism, 98(2), 1-5.

Kostoglou-Athanassiou, & Ntalles, K. (2010). Hypothyroidism: new aspects of an old disease. Hyppokkratia, 14(2), 82-87.

Mulryan, C. (2010). Disorders of the thyroid function. British Journal of Healthcare Assistants, 4(5), 218-222.

Shames, R. (2012). Diagnostic challenges and treatment options for thyroid conditions. Alternative and Complementary Therapies, 18(1), 8-13.

Synthroid. Synthroid information page [drug information page]. (2014, November 10). Retrieved from