Which Medications Can Cause Hyperthyroidism?

Hyperthyroidism occurs in around 1 out of every 100 people over the age of 12 in the US.¹ The condition is characterized by elevated levels of thyroid hormones. While there are several potential causes for hyperthyroidism, including Graves' disease and overactive thyroid nodules, certain medications may also lead to the condition.

Learn more about these medications, why they increase the risk of developing hyperthyroidism, and when you should see a doctor about your symptoms.

What is hyperthyroidism?

The thyroid gland is a butterfly-shaped gland that sits in front of your larynx near the base of your neck. It secretes thyroid hormones, which your body uses to store and manage energy. These hormones have an impact on functions such as heart rate, respiration, and metabolism.

Sometimes, the thyroid gland will secrete too much thyroid hormone. This is hyperthyroidism, also known as an overactive thyroid. Having an elevated level of thyroid hormone in your system can cause side effects such as: 

• Increased appetite

• Unexplained weight loss

• Feeling more sensitive to heat 

• Needing to defecate more often

• Muscle tremors, especially in the hands

• An increased heart rate

• Irritability or anxiety

• Being unable to sleep or feeling tired after a long night's rest

The symptoms of hyperthyroidism can range from very mild to debilitating. If left untreated, hyperthyroidism can increase the risk of stroke and other heart-related issues.² It can also lead to osteoporosis³ and have a detrimental effect on both male and female fertility.⁴ Some people may also develop a condition called Graves' ophthalmopathy, which affects the eyes.

With the right treatment options, most people diagnosed with hyperthyroidism can live healthy, happy lives. 

Are there medications that cause hyperthyroidism?

There are many different causes of hyperthyroidism. Graves' disease is the most common one, but certain medications may also cause it.

These medications include:

• Amiodarone: This medication is primarily used to treat heart rhythm disorders. It contains around 100 times the typical daily intake of iodine. The thyroid gland uses iodine to produce hormones, and an increased amount of iodine can cause the thyroid gland to become overactive.

• Interferon-alpha: This medication is used to treat chronic hepatitis C virus (HCV) infections. Around 15% of people who take this medication develop thyroid disease.⁵ While this may be due to the medication itself, there are also indications that HCV may play a role in causing the development of hyperthyroidism.

• Programmed death receptor-1 (PD-1) inhibitors: PD-1 inhibitors are used in cancer immunotherapy, working to help the body's natural defense system to fight cancer cells. They also increase the risk of developing hyperthyroidism.⁶ The medication causes the release of antibodies that work against thyroid hormones.

• Alemtuzumab: This is another drug for the treatment of cancer. Patients who take this medication are especially susceptible to developing Graves' disease,⁷ one of the most common causes of hyperthyroidism. This happens when the body creates antibodies that attack the thyroid gland.

• Lithium: This is used to treat bipolar disorder. Rarely, it may cause the development of hyperthyroidism or Graves' disease. It does this by increasing the thyroid gland's ability to use and retain iodine, which is needed to create thyroid hormones.

Certain over-the-counter medications and supplements may also cause hyperthyroidism. This typically happens when the medication or supplement contains a lot of iodine, such as in sea kelp supplements.

If you are experiencing any symptoms of hyperthyroidism, it's important to tell your doctor about all the medications you are taking. This includes over-the-counter, non-prescription medications as well as dietary supplements.

Can thyroid medication cause hyperthyroidism?

Yes. If you are taking thyroid medication to treat hypothyroidism, also known as an underactive thyroid gland, you may develop hyperthyroidism if you end up taking too much of your thyroid medication.

Your thyroid hormone levels can fluctuate over time, due to lifestyle changes, the introduction of more iodine in your diet, or the progression of a medical condition. Your doctor will monitor your thyroid levels regularly and adjust your thyroid medication accordingly.

However, if you are currently on thyroid medication and notice symptoms associated with hyperthyroidism, make an appointment with your doctor. They can evaluate your thyroid hormone levels and adjust your medication.

Other possible causes and risk factors for hyperthyroidism

While certain medications could put you at risk of developing hyperthyroidism, some factors may also increase your risk of developing the condition. These include:

• A family history of thyroid disorders 

• Having certain medical conditions such as pernicious anemia or diabetes

• Being over the age of 60 

• Having had a goiter, or swollen thyroid gland, which was treated in the past 

• Having been pregnant within the last six months

When to see a doctor about your symptoms

If you are experiencing any symptoms of hyperthyroidism, make an appointment with your primary care provider. They can help diagnose hyperthyroidism with a simple blood test that measures your thyroid hormone levels.

If your hormone levels are raised, your doctor will discuss treatment options with you to bring them back into a normal range.

There are many treatment options available for hyperthyroidism, including:

• Medication

• Radioiodine therapy

• Surgery

The lowdown

Hyperthyroidism, also known as an overactive thyroid gland, happens when the thyroid gland produces too much thyroid hormone. This can cause symptoms such as rapid heart rate, unexplained weight loss, and hand tremors. Certain medications can increase the risk of developing hyperthyroidism. 

If you are experiencing any symptoms of hyperthyroidism, make an appointment with your primary care provider. Be sure to tell them about any medications you are taking, including dietary supplements. They can diagnose hyperthyroidism through a simple blood test and discuss your treatment options with you.