Medications Used to Treat Thyroid Disease

Thyroid medications encompass an array of different options, which differ not only in their composition but their intent. Hormone replacement therapy, such as Synthroid (levothyroxine), is the most widely used drug for hypothyroidism. An anti-thyroid drug like Tapazole (methimazole) may be used for hyperthyroidism, and thyroid cancer patients may require or radioactive-iodine therapy or chemotherapy.

They all, however, have one thing in common: Treatment with them must be optimized in order to adequately manage your thyroid disease.

The role of the thyroid gland is to produce the hormones thyroxine (T4) and triiodothyronine (T3). These thyroid hormones regulate everything from heart rate and body temperature to respiratory function and a woman’s menstrual cycle.

When the thyroid gland becomes underactive—from Hashimoto's disease (an autoimmune disorder), iodine deficiency, or surgical removal of the thyroid gland, among other causes—an insufficient amount of thyroid hormone is produced, leading to a variety of symptoms that affect one or more organ systems and range in severity from mild to debilitating.

In order to restore sufficient thyroid hormone levels in the body, everyone with hypothyroidism must take thyroid hormone replacement medication—exceptions include those whose underactive thyroid gland is transient (e.g., thyroiditis) or reversible (e.g., caused by a drug that can be discontinued).

There are four main goals of thyroid hormone replacement medication:

• Alleviate symptoms of hypothyroidism
• Normalize the thyroid stimulating hormone (TSH) level
• Reduce the size of an enlarged thyroid (goiter) if present
• Avoid overtreatment (becoming hyperthyroid)

Levothyroxine—also called l-thyroxine and L-T4—is a synthetic form of the T4 (thyroxine) hormone. T4 is the storage hormone, and it must be converted into T3, the active hormone, to be used by your cells.

Levothyroxine is the drug of choice for the treatment of hypothyroidism. In the United States, brand names are Synthroid, Levoxyl, Unithroid, and Tirosint.

Liothyronine is a synthetic form of T3 (triiodothyronine). Brand names of liothyronine in the United States are Cytomel and Triostat.

Due to the fact that experts, for the most part, recommend T4-monotherapy and not combination T4/T3 therapy for treating hypothyroidism, this medication is not commonly prescribed.

Research is ongoing about whether combination T4/T3 therapy may benefit a subgroup of people with hypothyroidism who have a certain genetic mutation. Keeping abreast of this research is valuable, as it may alter your thyroid care in the future.

Natural desiccated thyroid—also known as NDT, natural thyroid, or porcine thyroid,—is a prescription drug derived from the dried thyroid glands of pigs. NDT contains both T4 and T3.

Common brands are Armour Thyroid and Nature-throid, and a generic is also available.

Most endocrinologists and many mainstream physicians do not support or prescribe the use of natural desiccated thyroid drugs; this is because they are combination drugs and because the ratio of T4 to T3 does not match up to the ratio of T4 to T3 in humans. That said, certain select patients may respond well to NDT.

Hyperthyroidism means the thyroid gland is overactive, producing too much thyroid hormone. There are multiple causes of hyperthyroidism including Grave’s disease (another type of autoimmune disorder), non-cancerous thyroid nodules, thyroid inflammation (thyroiditis), and a malfunctioning pituitary gland (which works in tandem with the thyroid gland). Moreover, a phase of Hashimoto’s disease can also cause hyperthyroidism in the same way that it causes hypothyroidism.

The treatment of hyperthyroidism is generally more complex than hypothyroidism, requiring one or more of the following treatments:

• Anti-thyroid drug
• Radioactive iodine (RAI)
• Surgery to remove the gland (thyroidectomy) 

The only "medications" for hyperthyroidism are anti-thyroid drugs. There are currently two approved for use in treating hypothyroidism in the United States.

• Tapazole (methimazole, or MMI)
• Propylthiouracil (PTU)

The antithyroid drug Tapazole inhibits the thyroid from using iodine—usually from the diet—to produce thyroid hormone. It is a medication that is generally taken once a day by patients. Tapazole has fewer side effects and reverses hyperthyroidism more quickly than PTU, making it the preferred anti-thyroid drug choice.

PTU inhibits the thyroid gland form using iodine, thus slowing the overproduction of thyroid hormone. It also inhibits the conversion of thyroid hormone T4 into T3. PTU has a short-acting timespan, so patients taking this medication usually are instructed to take the medication two to three times per the day to effectively lower thyroid hormone levels.

PTU has more side effects than the other drugs discussed here. It is the preferred drug for hyperthyroidism only in a few situations—early pregnancy, severe thyroid storm, and in the event a patient is experiencing serious side effects from methimazole.

Beta-blockers, like Inderal (propranolol), are not used to "treat" hyperthyroidism, but rather to reduce the symptoms of excess thyroid hormone on the body like a fast heart rate, tremor, and anxiety.

The primary treatment for most thyroid cancers is surgery with removal of the entire thyroid gland (total thyroidectomy) or a lobe of the thyroid gland (lobectomy).

After surgery, patients will require thyroid hormone replacement medication (levothyroxine) to replace thyroid hormone production and suppress tumor regrowth.

Levothyroxine is used to treat hypothyroidism due to thyroid surgery for cancer just as it is used for other cases of underactive thyroid. Depending on the extent of the disease and the person's risk for recurrent thyroid cancer, a doctor will determine what range TSH should be suppressed to and adjust the levothyroxine accordingly.

For large thyroid cancers, a thyroid cancer that has spread to the lymph nodes, and/or if you are considered high risk for recurrent cancer, radioiodine therapy may be given after surgery.

The radioactive iodine is given is given in a hospital setting in either liquid form or as a capsule. Its main goal is to kill off cancer cells that remain after surgery and destroy any remaining thyroid tissue.

Chemotherapy, which works by killing rapidly dividing cells, like cancer cells, is not often used to treat thyroid cancer unless a person has recurrent and/or metastatic cancer. Chemotherapy is also combined with external beam radiation for the treatment of a rare type of thyroid cancer called anaplastic thyroid cancer.

Scientists have developed several drugs called "targeted therapies" that target specific markers on cancer cells. Some of these drugs have been used to treat advanced or resistant thyroid cancer.

Nexavar (sorafenib) and Lenvima (lenvatinib) are two targeted therapies—kinase inhibitors that work partially by blocking thyroid cancers from growing and making new blood vessels.

No doubt, being diagnosed with a thyroid condition can be overwhelming. But by gaining knowledge about the medications used to treat your disease, you are already taking the first step in your care.

Keep in mind, as you continue on your thyroid journey, you are not alone—and for most of you, your condition can be either cured or managed well. Don't hesitate to update your doctor on how you are feeling. There are many cases in which a patient might benefit from an adjusted dose or even a drug change.