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Running head: LEVOTHYROXINE
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Use of Levothyroxine in Hypothyroidism Treatment
Dacy Gaston
South University
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Use of Levothyroxine in Hypothyroidism 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 hypothyroidism is 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 treating primary 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 treating hypothyroidism.
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
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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 has common physical symptoms such as depression, weight gain,
dry hair, dry skin and fatigue; and clinical 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 evaluation by 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
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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
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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
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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.
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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.
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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.
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Self-management and education for the hypothyroid patient can improve adherence and lead to a
successful euthyroid state for this patient population.
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References:
American Thyroid Association. (2014). What is Hypothyroidism? Retrieved from
http://www.thyroid.org/wp-content/uploads/patients/brochures/Hypo_brochure.pdf
American Association of Clinical Endocrinologists. (2012). Clinical Practice Guidelines for
Hypothyroidism in Adults. Retrieved from
https://www.aace.com/files/checklists_july_2014_ep.pdf
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.
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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).
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