Oral Treatments for Hypothyroidism

The thyroid gland makes hormones that are necessary for growth and development in children, and for regulating energy levels at all ages. When the thyroid does not produce sufficient thyroid hormones, the condition is known as hypothyroidism, also known as underactive thyroid.

Hypothyroidism is the most common thyroid disorder, affecting nearly 5 percent of the U.S. population age 12 and older.[1] The major cause of the disorder is autoimmune disease (mainly Hashimoto’s thyroiditis). Other causes include surgical removal of the thyroid (due to cancer or other diseases) and radioactive iodine or other types of radiation treatment.[2]

Individuals with hypothyroidism may have symptoms such as mental fogginess, low energy, slow heartbeat, feeling chilled, aching muscles, weight gain, constipation, hair loss and dry skin. Because these symptoms can have several other causes, health care providers rely on blood tests to properly diagnose hypothyroidism.

Although there is no known cure for hypothyroidism, there are several medications on the market for “replacing” the missing natural thyroid hormones, relieving symptoms and restoring normal energy levels. These medications are given orally, although some can be given by injection in emergency situations.

Not all thyroid hormone replacement medications are the same, and some are not even approved for use in the U.S. Learn which of these medications you should take — and which ones you should not take — to treat hypothyroidism.

Levothyroxine (LEVO-T, LEVOXYL, SYNTHROID, TIROSINT, UNITHROID)

Levothyroxine is the most commonly prescribed drug to treat hypothyroidism,[3] as well as the thyroid hormone replacement drug that is recommended by the American Association of Clinical Endocrinologists and the American Thyroid Association.[4] It is a synthetic (lab-made), but identical, form of the inactive human thyroid hormone thyroxine (or T4). It comes in various formulations with a dozen different strengths. The body converts it to triiodothyronine hormone (or T3), which is the predominant active hormone used by the body.

Forty to 80 percent of the drug is absorbed after oral intake. The drug is slowly processed by the body, which makes it ideal for once-daily dosing.[5] The starting dose depends on patient factors, such as age, weight, use of other medications and the presence of heart disease. Extra caution to avoid overdosing is needed for the elderly and patients with heart disease.

The dose initially is adjusted every four to six weeks, based on thyroid blood test results along with patient symptoms, until an optimal steady (maintenance) dose is reached. Once a stable effective dose is achieved, thyroid blood tests should be checked annually.[6]

Some endocrinologists were concerned in the early 2000s about differences in the potency of levothyroxine products over time.[7] As a result, the Food and Drug Administration (FDA) in 2007 established new requirements for all levothyroxine products to ensure that they remain stable over their entire shelf lives.[8] The agency also concluded that approved generic products are as effective as brand-name products. However, the American Thyroid Association still advises patients to use the same brand or generic formulation throughout treatment and to have thyroid function tests checked after any change in drug formulation.[9]

Levothyroxine’s side effects are the same as those associated with other thyroid hormone drugs. They are usually caused by overtreatment, which results in symptoms of hyperthyroidism (overactive thyroid). Cardiovascular complications[10] (irregular heartbeat, chest pain or even heart attack) are the most serious side effect. Osteoporosis (bone loss) can also occur if high doses are taken for a long time, increasing the risk of fractures. Other side effects include rapid heart rate, palpitations, tremors, anxiety, sweating and weight loss.

Liothyronine (CYTOMEL)

Liothyronine is the synthetic version of the most active thyroid hormone (T3).[11] It is almost totally absorbed within four hours after oral intake, resulting in a sudden high drug level in the blood, which can lead to more side effects than seen with levothyroxine.[12] But liothyronine drug levels then fall off rapidly within hours, which means that the drug does not have steady levels in the blood throughout the day. This makes it necessary to take multiple daily doses to maintain the drug’s effect.[13] Another concern about taking this drug is that the body no longer naturally regulates the conversion of T4 to T3 according to its needs. The American Thyroid Association does not recommend the use of this drug to treat hypothyroidism.

Public Citizen’s Health Research Group classifies this drug as Limited Use — a designation that we give to drugs that offer limited benefit or benefit only certain people or conditions. We do not recommend it for the maintenance (long-term) treatment of hypothyroidism.

Liotrix (THYROLAR)

This drug contains a combination of levothyroxine and liothyronine. Because it contains much more liothyronine than is naturally produced in the body, this drug is subject to the same problems as liothyronine-only treatment.

There has been interest among some patients and doctors about whether this drug, or a combination of the individual levothyroxine and liothyronine drugs, can be used on a trial basis in the small subset of patients who still have symptoms on levothyroxine only. However, this approach is not recommended by the American Thyroid Association’s Task Force on Hormone Replacement Therapy, due to the lack of evidence to support its long-term effectiveness or safety.[14] We do not recommend this drug as a maintenance therapy for hypothyroidism and classify it as Limited Use.

Desiccated (dried and powdered) thyroid extracts

Also known as thyroid USP (ARMOUR THYROID, NATURE-THROID, NP THYROID, WESTHROID, WP THYROID), these products contain a mixture of levothyroxine and liothyronine hormones that are obtained from pig thyroid glands.[15] Unlike synthetic thyroid hormone products, thyroid extracts have never been reviewed or approved by the FDA.

These products are falsely promoted by their manufacturers as “natural,” ignoring the fact that they contain a much higher ratio of liothyronine to levothyroxine hormones than that in humans.[16] Such excess liothyronine content can lead to serious long-term cardiovascular and bone turnover risks.

Proponents of thyroid extracts frequently cite a short-term study that found that some patients may prefer these products.[17] However, there is no evidence to support any clinical advantages for these products over levothyroxine.[18] Equally importantly, there are no long-term studies that address the safety concerns related to the abnormally high blood liothyronine levels associated with these products.[19]

Therefore, the American Association of Clinical Endocrinologists and the American Thyroid Association advise against the use of these products.[20] Public Citizen’s Health Research Group has also long classified these products as Do Not Use.

What You Can Do

If you experience hypothyroidism symptoms, talk with your primary care provider about doing a thyroid blood test. If your primary care provider determines that you have hypothyroidism and need thyroid hormone replacement therapy, opt for levothyroxine and try to stay on the same drug formulation. Always take levothyroxine at least 30 minutes before meals at the same time every day, preferably before breakfast. Never stop this drug, skip a dose or adjust your dose without medical supervision.

Do not use liothyronine and liothyronine-containing drugs as a maintenance treatment of hypothyroidism, because there is no long-term evidence supporting their efficacy or safety relative to levothyroxine-only treatment. Avoid thyroid extracts because they are not regulated, effective or safe, despite the push for their use by some misinformed “natural product” enthusiasts.

References

[1] Hollowell J, Staehling N, Flanders W, et al. Serum TSH, T(4), and thyroid antibodies in the United States population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab. 2002;87(2):489-499.

[2] American Thyroid Association. Hypothyroidism. 2014. http://www.thyroid.org/wp-content/uploads/patients/brochures/ata-hypothyroidism-brochure.pdf. Accessed September 16, 2016.

[3] Symphony Health Solutions. Top 200 drugs for 2014. 2015. http://symphonyhealth.com/wp-content/uploads/2015/05/Top-200-Drugs-of-2014.pdf. Accessed September 16, 2016.

[4] Garber JR, Cobin RH, Garib H, et al. Clinical practice guidelines for hypothyroidism in adults: Cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012;18(6): 988-1028.

[5] Lannett Company Inc. Label: levothyroxine sodium. March 2012. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=99aebc74-0e34-4ab3-bb59-d9fb2b9a4444. Accessed September 16, 2016.

[6] American Thyroid Association. Hypothyroidism. 2014. http://www.thyroid.org/wp-content/uploads/patients/brochures/ata-hypothyroidism-brochure.pdf. Accessed September 16, 2016.

[7] Food and Drug Administration. Thyroid Medications: Q & A with Mary Parks, M.D. January 2008. http://www.fda.gov/forconsumers/consumerupdates/ucm107377.htm. Accessed September 16, 2016.

[8] Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism. Thyroid. 2014;24(12):1670-1751.

[9] American Thyroid Association. Thyroid Hormone Treatment. 2014. http://www.thyroid.org/wp-content/uploads/patients/brochures/HormoneTreatment_brochure.pdf. Accessed September 16, 2016.

[10] Garber JR, Cobin RH, Garib H, et al. Clinical practice guidelines for hypothyroidism in adults: Cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012;18(6): 988-1028.

[11] Mylan Pharmaceuticals Inc. Label: Liothyronine sodium. January 2013. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0a2215ba-fdc1-4439-b4c5-679933c4a6fb. Accessed September 16, 2016.

[12] American Thyroid Association. Thyroid Hormone Treatment. 2014. http://www.thyroid.org/wp-content/uploads/patients/brochures/HormoneTreatment_brochure.pdf. Accessed August 22, 2016.

[13] Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: Prepared by the American Thyroid Association task force on thyroid hormone replacement. Thyroid. 2014;24(12):1670-1751.

[14] Ibid.

[15] Ibid.

[16] Ibid.

[17] Hoang TD, Olsen CH, Mai VQ, et al. Desiccated thyroid extract compared with levothyroxine in the treatment of hypothyroidism: A randomized, double-blind, crossover study. J Clin Endocrinol Metab. 2013;98(5):1982-1990.

[18] American Thyroid Association. Thyroid Hormone Treatment. 2014. http://www.thyroid.org/wp-content/uploads/patients/brochures/HormoneTreatment_brochure.pdf. Accessed August 22, 2016.

[19] Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: Prepared by the American Thyroid Association task force on thyroid hormone replacement. Thyroid. 2014;24(12):1670-1751.

[20] Garber JR, Cobin RH, Garib H, et al. Clinical practice guidelines for hypothyroidism in adults: Cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Oral Treatments for Hypothyroidism. 2012;18(6): 988-1028.