The thyroid gland is a butterfly-shaped gland in your neck that plays a key role in regulating your body’s metabolism. Normally, your thyroid produces hormones called thyroxine (T4) and triiodothyronine (T3). These hormones influence everything from your energy levels to your heart rate.
Hypothyroidism is a common endocrine disorder where the thyroid gland does not produce enough thyroid hormones. When thyroid hormone levels drop, your body slows down, leading to various symptoms. While the most frequent causes include Hashimoto’s thyroiditis (an autoimmune disease) and iodine deficiency, certain medications can also lead to what is known as drug-induced hypothyroidism.
In this article, we will learn about the causes, symptoms, and management of this condition.
What Causes Drug-Induced Hypothyroidism?
Medications can interfere with your thyroid function in various ways, leading to a decrease in thyroid hormone production. While some medications can directly hinder the thyroid’s ability to produce thyroid hormones, other drugs can also trigger an inflammation of the thyroid, temporarily affecting its function.
Here are some common medications that can cause hypothyroidism:
1. Lithium
Used to treat bipolar disorder, lithium can affect hormone production in up to 20% of patients taking it long-term. Lithium impacts the thyroid gland’s ability to take up iodine, which is essential for thyroid hormone production. It can also inhibit the release of thyroid hormones from the thyroid gland, leading to a build-up of colloid (a gel-like substance consisting mainly of thyroglobulin) in thyroid follicular cells and ultimately causing goiter formation in some cases.
2. Amiodarone
This medication is prescribed for heart rhythm problems. It is rich in iodine, comprising about 37% iodine by weight. The excess iodine released during the metabolism of amiodarone can disrupt normal thyroid function, known as the Wolff-Chaikoff effect, leading to an inhibition of thyroid hormone production and release.
3. Interferons
Used to treat some cancers and viral infections, interferons can stimulate the immune system in a way that promotes the development or exacerbation of autoimmune thyroid disorders, such as Hashimoto’s thyroiditis. They increase the production of cytokines and activate immune cells, which can lead to the development of thyroid antibodies attacking thyroid cells.
4. Tyrosine kinase inhibitors (TKIs)
Used in cancer treatment, TKIs can induce hypothyroidism through several mechanisms. TKIs may interfere with the thyroid gland’s ability to absorb iodine. They may also trigger inflammation in the thyroid gland, leading to cell damage and impaired hormone production. TKIs can also inhibit the activity of an enzyme (peroxidase) involved in thyroid hormone synthesis and as a result, reduce hormone production. The exact mechanism, however, can vary depending on the specific TKI.
What are the Symptoms of Drug-Induced Hypothyroidism?
The symptoms of drug-induced hypothyroidism mirror those of typical hypothyroidism and include:
- Fatigue and tiredness
- Feeling cold more often
- Feeling down or depressed
- Weight gain or difficulty losing weight
- Dry skin and hair
- Brittle nails
- Muscle aches and weakness
- Constipation
- Slow heart rate
- Irregular menstrual periods
How is Drug-Induced Hypothyroidism Diagnosed?
If you are experiencing symptoms and take medications that list thyroid dysfunction as a side effect, be sure to mention this to your doctor. A simple blood test can measure your thyroid hormone levels, necessary for diagnosing hypothyroidism.
In the same vein, the diagnosis of drug-induced hypothyroidism starts with a clinical evaluation of symptoms followed by some thyroid function tests. Elevated TSH and low T4 levels typically indicate hypothyroidism. Additionally, doctors assess a patient’s medication history to see if the patient has been exposed to drugs known to affect thyroid function.
If the patient is on a medication known to cause thyroid dysfunction, regular monitoring of thyroid function is recommended. The diagnosis is further supported if thyroid function improves after altering the medication regimen, thereby providing a causal link between the drug and hypothyroidism.
How is Drug-Induced Hypothyroidism Managed and Treated?
The good news is that drug-induced hypothyroidism is often treatable. The treatment approach, however, depends on the cause (the medication) and severity of the condition. Here are some possible approaches:
1. Adjusting Medication
The primary approach involves evaluating the necessity of the offending medication. If possible, your doctor may adjust the dose of the medication causing the problem or switch you to a different medication altogether. However, if the medication is essential and cannot be discontinued, other management strategies will be needed.
2. Thyroid Hormone Replacement
The most common treatment for drug-induced hypothyroidism is thyroid hormone replacement therapy, typically with levothyroxine. This treatment involves daily hormone intake to restore normal hormone levels, which usually alleviates the symptoms.
3. Regular Monitoring
Patients diagnosed with drug-induced hypothyroidism require regular monitoring of their thyroid function, especially if they continue to take the implicated drug. Periodic blood tests will help ensure that thyroid hormone levels remain within a normal range and that the treatment is effective.
Here are some additional tips:
- Keep a record of all medications you take, including over-the-counter drugs and supplements.
- Tell your doctor about any new medications you start taking.
- Ask your doctor if any medications you take can affect your thyroid.
- Don’t hesitate to discuss any concerning symptoms you experience.
Key takeaways
- As the name suggests, drug-induced hypothyroidism is a condition where a medication you’re taking disrupts your thyroid function, causing it to become underactive.
- Drugs like lithium, amiodarone, interferons, and tyrosine kinase inhibitors can induce hypothyroidism.
- Some of these drugs cause hypothyroidism by interfering with hormone production, triggering an autoimmune response, and triggering inflammation of the thyroid.
- If you take any medications that might affect your thyroid, be aware of the symptoms and talk to your doctor if you experience any concerns. Remember that drug-induced hypothyroidism is a manageable condition. It is even reversible if the implicated drug can be discontinued.
- Early diagnosis and appropriate treatment (or treatment adjustments) can help manage and potentially reverse drug-induced hypothyroidism
