Thyroid hormones: Uses, common brands, and safety info

Thyroxine is a hormone that our bodies naturally make to help with important functions for normal growth and development. Released from the thyroid gland, this hormone helps to regulate digestion, metabolic rate, muscle and heart function, brain development, body temperature, and bone health. Some people need more thyroxine than the body is able to make due to thyroid disease and can be prescribed thyroxine medications. These people may include those with hypothyroidism, enlarged thyroid gland, a removed thyroid, or thyroid cancer.

Let’s take a look at the main uses, common brand names, and safety information for thyroxine medications.

The most common need for thyroid hormone replacement medications is the thyroid disorder hypothyroidism, which is when a person does not make enough thyroxine (also called tetraiodothyronine or thyroxin). This can be due to autoimmune diseases, certain medications, or not enough iodine consumption.

A potential autoimmune disease a person with low levels of thyroxine could have is Hashimoto’s disease. Those with Hashimoto’s disease experience the effects of their immune system attacking the thyroid. Signs of Hashimoto’s disease may start with swelling in the front of the throat (a goiter) and slowly progress with symptoms of hypothyroidism.

Signs of hypothyroidism include the following:

• Fatigue

• Increased sensitivity to cold

• Constipation

• Pale, dry skin

• Puffy face

• Brittle nails

• Hair loss

• Enlargement of tongue

• Unexplained weight gain

• Muscle aches, tenderness, and stiffness

• Joint pain and stiffness

• Muscle weakness

• Excessive or prolonged menstrual bleeding

• Depression

• Memory lapses

There are certain medications that could lower the level of thyroxine in the body such as the following:

• Lithium

• Methimazole

• Amiodarone

• Propylthiouracil

• Interferons

• Glucocorticoids

• Dopamine agonists

• Somatostatin analogs

• Rexinoids

Iodine is a trace element and is important for helping the body make thyroxine. This element is taken up into cells and through a series of enzymes becomes a precursor to thyroid hormones. Iodine is often added to salt, which is referred to as iodized salt and can be found naturally in a variety of foods including seaweed, seafood, and eggs. Aside from food, iodine is available as a supplement and included in multivitamins to help prevent iodine deficiency.

What are thyroid hormones?

Thyroid hormone medications are either synthetic or animal product forms of hormones the body normally makes. As part of the body’s endocrine system, thyroxine is one of two hormones made from thyroglobulin that the thyroid gland produces and is referred to as T4. The second hormone is called triiodothyronine, T3. When people have hyperthyroidism, such as Grave’s disease, they will have too high levels of thyroid hormones. Both of these thyroid hormones are essential for the body’s functions and available in medication form.

Thyroxine is available as a synthetic medicine called levothyroxine and is most commonly used to treat low thyroxine levels. Triiodothyronine is available as a synthetic medicine called liothyronine. There are combination forms available that contain both thyroxine and triiodothyronine. Additionally, there are animal products called desiccated thyroid that contain both thyroid hormones. The desiccated thyroid form typically comes from the dried thyroid of porcine (pig).

How do thyroid hormones work?

Thyroxines (T4), triiodothyronine (T3), and desiccated thyroid medications work to replace the thyroid hormone levels that can be missing in the body. For patients taking T4 or combination products, the body can undergo synthesis of T4 into the active form T3 to help replace both hormones. Once taken by the patient, these hormone replacements circulate in the body and attach to receptors to help with normal growth and development.

In order to make sure the amount of replacement therapy is correct, a healthcare provider or endocrinologist will have the patient give a blood sample to test the levels of thyroid hormones in the body. There are a variety of thyroid function tests available, but often the tests performed measure TSH (thyroid-stimulating hormone) and T4 (bound and free thyroxine levels). As a gland that controls a majority of the body’s hormone secretions, the pituitary gland produces TSH that regulates the amount of thyroid hormones.

The thyroid function tests and diagnosis can help determine what type of thyroid medication is most appropriate for the patient. Additionally, these patients will regularly have blood tests to make sure they are receiving the correct dose of medication.

While there are many brand name medications available that contain T3, T4, or a combination of the two, it is important for patients to stay with the same brand name throughout therapy. These medications will have different inactive ingredients and regularly switching between brand names can affect the level of thyroid hormones in the body.

What are thyroid hormones used for?

• Hypothyroidism

• Pituitary thyrotropin suppression

• Enlarged thyroid gland (goiter) due to underactive thyroid

• Adjunct to certain thyroid cancers

Types of thyroid hormone replacements

Thyroxine

Thyroxine is available as a synthetic form called levothyroxine and is the preferred choice for treating hypothyroidism based on current guidelines and clinical trials. As a synthetic preparation, the amount of thyroxine is more precise than animal forms. Levothyroxine is available as a generic medication and in a variety of brand names including Synthroid, Levoxyl, and Unithroid. Levothyroxine replaces the thyroxine (T4) the body normally makes. After about six weeks of therapy, a person should notice improvements in symptoms of low thyroid levels. Levothyroxine comes in several forms including tablets, capsules, and liquid solution. Doses of levothyroxine are individualized and depend on a person’s thyroid function tests. Typically, the levothyroxine dose is between 50 to 200 mcg per day.

Triiodothyronine

Triiodothyronine (T3) is available as a synthetic form called liothyronine. As a synthetic form, the amount of triiodothyronine is more accurate than animal forms. Liothyronine is available as a generic medication and as the brand name Cytomel. Liothyronine has a faster onset of action and a shorter half-life than levothyroxine. Liothyronine comes in a tablet and doses will be customized based on the person’s thyroid function tests. Typically, the liothyronine dose is between 25 to 75 mcg per day.

T3 and T4 Combination

Thyroxine and triiodothyronine are available as a synthetic combination medication called Liotrix. This combination contains a 4:1 mixture of T4 (levothyroxine) and T3 (liothyronine) to help replace these hormones that the body normally makes. As a synthetic preparation, the amounts of thyroxine and triiodothyronine are more precise than animal forms. Liotrix is available as a tablet and the dose will be determined by the thyroid function tests. Typically, the Liotrix dose is levothyroxine 50-100 mcg/liothyronine 12.5-25 mcg per day.

Desiccated Thyroid

Both thyroxine (T4) and triiodothyronine (T3) are available as a natural form in desiccated thyroid medications. Synthesized from the dried thyroids of animals, this form helps replace both T4 and T3 normally found in the body. Desiccated thyroid is available as several brand name medications including Armour Thyroid, Nature-Throid, NP Thyroid, Westhroid, and WP Thyroid. These desiccated thyroid medications are available as a tablet and can have variations in the amount of T4 and T3 since they are from animal product. Because of variability, a person’s T4 and T3 blood levels can differ between new prescription bottles. These tablets have a characteristically strong odor. Since these are typically made from pigs, it is important for people of certain religions that do not consume any pig products to speak with a doctor about any concerns. Typically, the desiccated thyroid dose is 60 to 120 mg per day.

Who can take thyroid hormones?

Thyroid hormone are generally safe medications for most people. Both adults and children can be prescribed these medications. However, there are a few groups of people who require extra caution and monitoring if using these medications.

Seniors

Caution must be taken when using any thyroid replacement medication in people 65 and older. Seniors have a greater chance of developing cardiac reactions including dangerous chest pain or changes in heart rate. For this reason, the starting recommended dose is lower for seniors.

People with underlying cardiovascular disease 

For those with cardiovascular disease, caution should be taken when using any thyroid replacement medication. These include people with high blood pressure, congestive heart failure, a previous heart attack or stroke, heart arrhythmias, and coronary artery disease. Having cardiovascular disease puts these patients at a higher risk of developing cardiac reactions. It is recommended that these patients start at a lower dose.

Are thyroid hormone safe?

Recalls

As of May 2021, there are no current recalls. The FDA regularly updates recalls for medications. These recalls are usually corrected to ensure patients have safe medications at home and are not dispensed recalled medication at pharmacies.

Restrictions

All thyroid hormone replacement medications have a black box warning stating they are not intended for the treatment of obesity or weight loss. Despite these medications often causing weight loss as a side effect, there are dangers associated with taking too much thyroid hormone replacement.

There are some conditions that are restricted with the use of thyroid hormone replacement medications. These conditions include people with uncorrected adrenal insufficiency, untreated thyrotoxicosis, and allergies to any of the ingredients.

Can you take thyroid hormones while pregnant or breastfeeding?

Thyroxines and other thyroid hormone replacement medications are safe for pregnant women, however, levothyroxine is the preferred choice for pregnant women with hypothyroidism. The dose of medication may need to be adjusted as the levels of thyroid hormones can fluctuate during pregnancy. Additionally, breastfeeding is safe for women taking levothyroxine.

Are thyroid hormones controlled substances?

No, thyroxines and other thyroid hormone replacement medications are not controlled substances.

Common thyroid hormone side effects

Side effects usually happen if the dose of hormone replacement is too high. The types of side effects are very similar between the thyroid hormone replacements. If people experience side effects, their healthcare provider can reevaluate the dose and make adjustments based on their thyroid function tests.

Some common levothyroxine, liothyronine, and desiccated thyroid side effects include:

•       Heart palpitations

•       Increase in appetite

•       Fast heartbeat

•       Nervousness

•       Tremor

•       Weight loss

•       Sweating

•       Diarrhea

•       Abdominal cramps

•       Insomnia

•       Fever

•       Headache

•       Hair loss

•       Heat intolerance

•       Menstrual irregularities

•       Nausea

•       Anxiety

•       Shortness of breath

•       Rash

•       Muscle spasm

•       Tremor

How much do thyroid hormones cost?

The price of thyroxines and thyroid hormone replacement medications varies based on if the medication is brand or generic and synthetic or animal product. The prices for a month's supply can range from $22 to $88. Typically, the animal product medications are less expensive than synthetic versions. Generic medications are often less expensive than brand-name medications.

It is best to speak with a healthcare provider about treatment options and review insurance coverage before starting therapy. A great option is to utilize a free prescription discount card from SingleCare.