Written by Megan N. Freeland, PharmD, RPh | Reviewed by Maria Robinson, MD, MBA Updated on March 23, 2023
Key takeaways:
- Certain medications, like amiodarone and lithium, can cause drug-induced hypothyroidism (low levels of thyroid hormone).
- When starting these medications, your healthcare provider can monitor your blood work to see if your thyroid is affected.
- Levothyroxine and close monitoring can treat drug-induced hypothyroidism.
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Healthcare providers call it “drug-induced hypothyroidism.” Simply put, it’s what happens when a medication you’re taking causes your thyroid gland to be less active than it should be.
So, should you be concerned that one of your medications might be making your thyroid gland less active? This article explores the most common medications that can cause hypothyroidism — and what you and your healthcare provider can do to fix it.
How do some medications cause hypothyroidism?
The thyroid gland uses iodine to make two chemicals — thyroid hormones T3 and T4 — that help your body control important processes like heart rate, temperature, and metabolism. When the nearby pituitary gland releases thyroid-stimulating hormone (TSH), it tells the thyroid gland to send more T3 and T4 into the rest of the body.
Usually, medications that cause hypothyroidism directly affect your TSH, T3, and/or T4 levels in some way. Some of them also cause thyroiditis — inflammation of the thyroid gland — which can change your TSH, T3, or T4 levels, too.
8 drugs that cause hypothyroidism
Here are eight medications that may lead to hypothyroidism.
1. Hyperthyroidism medications
Hyperthyroidism medications include propylthiouracil (PTU), methimazole, radioactive iodine (or radioiodine), and potassium iodine. Each of these medications is used to treat hyperthyroidism — a condition where you make too much thyroid hormone.
As a side effect, they can make thyroid hormone levels drop too low. The iodine-containing medications, specifically, cause the thyroid gland to shrink so that it produces less thyroid hormone. It’s important to find a balance where your levels aren’t too high or too low.
2. Amiodarone
People take amiodarone (Pacerone, Cordarone) to make their heart beat more regularly. Amiodarone contains a lot of iodine (almost 40%). It can cause hypothyroidism in two main ways: It can directly block T3 from being formed, and it can block the body’s signal to make T3 and T4. You’re more likely to develop hypothyroidism from amiodarone if your thyroid gland isn’t in great shape.
3. Lithium
Lithium is used to treat bipolar disorder. Hypothyroidism caused by lithium is most likely to happen early on in treatment. It’s also more likely to occur in women who are over 45 years old and people with a family history of hypothyroidism.
In fact, the older you are, the more likely you are to experience hypothyroidism after taking lithium. In some cases, you might notice symptoms from these thyroid changes. In others, your healthcare provider may just notice changes in your thyroid test values.
4. Interleukin-2
Interleukin-2 is usually used to treat cancers or leukemia. A small percentage of people taking this medication develop thyroiditis, which can lead to hypothyroidism.
5. Interferon alfa
Interferon alfa is used to treat leukemia, melanoma, non-Hodgkin’s lymphoma, and Kaposi’s Sarcoma. It also treats hepatitis C, hepatitis B, and human papillomavirus (HPV). It’s more likely to change thyroid function the longer you take it.
In addition to causing thyroiditis, this medication tells the body to make antibodies that fight the thyroid gland. Up to 15% of people who develop these antibodies will have thyroid diseases like hypothyroidism.
6. Tyrosine kinase inhibitors
Have you heard of tyrosine kinase inhibitors (TKIs)? This class of medications is used to treat different types of cancers and leukemias. Examples include sunitinib (Sutent) and sorafenib (Nexavar). Up to 40% of people who take a TKI will develop hypothyroidism. Studies show that this can happen anywhere from a few weeks to several months after starting the medication.
7. Checkpoint inhibitors
Checkpoint inhibitors are used to help the body fight cancer tumors. Examples include nivolumab (Opdivo), pembrolizumab (Keytruda), and ipilimumab (Yervoy). They cause changes in many different hormones throughout the body — including thyroid hormones. In studies, anywhere from 4% to almost 14% of people taking these medications had hypothyroidism. The risk was greatest with combination therapy.
8. Thalidomide
Though uncommon, there have been reports of people developing hypothyroidism due to thalidomide therapy. But healthcare providers don’t know exactly how it happens yet. Thalidomide is used to treat many different conditions, including multiple myeloma and leprosy.
How do you treat drug-induced hypothyroidism?
Most of the medications in this article are pretty important. So it’s not always feasible to stop the medication just because your thyroid levels are low. But since your thyroid health is important, you may have to replace those missing hormones. In that case, your healthcare provider may prescribe a medication like levothyroxine (Synthroid). This is a synthetic version of the T4 that mimics the natural T4 hormone and can replace what your body is missing.
You’ll also have your thyroid function checked regularly if you’re taking one of these medications. Your provider may check your thyroid tests after about 2 months of starting the medication. Then they’ll check at least every 6 to 12 months to make sure your thyroid is still healthy.
The bottom line
Certain medications can cause drug-induced hypothyroidism — low levels of thyroid hormones. Common culprits include amiodarone, lithium, and certain cancer medications like tyrosine kinase inhibitors. When starting any of these medications, your provider can check blood work to make sure your thyroid isn’t affected. If you do develop drug-induced hypothyroidism, levothyroxine and close monitoring of your blood work can treat it.
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