What Drugs Affect Thyroid Function?

Thyroid hormones regulate metabolism, growth, development, and energy production in every cell in our body. 

What Drugs Affect Thyroid Function?

They also play a key role in regulating blood pressure, heart rate, and brain activity.

If your thyroid isn’t working properly, you may experience symptoms such as fatigue, depression, hair loss, or weight gain.

Thyroid hormones are produced by the thyroid gland located at the base of the neck. 

The thyroid produces two types of hormones: thyroxine (T4) and triiodothyronine (T3).

T4 converts into T3 in the bloodstream. This hormone regulates metabolic processes throughout the body.

Drugs can interfere with the way your thyroid functions. Some medications cause hypothyroidism, which means your thyroid gland does not produce enough hormones. 

Other medications can cause hyperthyroidism, which means too much thyroid hormone is circulating in the bloodstream.

This article will discuss the types of drugs that can affect thyroid function.

What Is The Thyroid?

The thyroid is a butterfly-shaped organ that sits on top of the windpipe. It’s about the size of an almond.

The thyroid produces three hormones: thyroxine, triiodothyronine, and calcitonin. These hormones control how quickly cells use oxygen to break down food for energy.


Hypothyroidism occurs when the thyroid doesn’t make enough hormones. Symptoms include tiredness, constipation, dry skin, and weight gain. 

Hypothyroidism usually develops gradually over time.

People who have had thyroid surgery or radiation therapy are more likely to develop this condition than people without any history of these treatments.


Hyperthyroidism occurs when the body makes too much thyroid hormone.

Symptoms include irritability, nervousness, rapid heartbeat, high blood pressure, sweating, and weight loss. 

In most cases, hyperthyroidism is caused by Graves’ disease – an autoimmune disorder where the immune system attacks the thyroid.

Which Drugs Can Affect The Thyroid?

There are many different classes of drugs that can affect the thyroid. Many of them are used to treat other conditions. 

For example, beta-blockers are commonly prescribed to lower blood pressure. However, they can sometimes cause low thyroid levels.


Beta-blockers slow the electrical signals sent from the nerves to the muscles. These drugs work well to treat hypertension, but can sometimes lead to an underactive thyroid.


Lithium is often prescribed to treat bipolar disorders. Lithium helps stabilize mood swings and reduce suicidal thoughts. But it can also cause problems with the thyroid.


Many antidepressants can cause low thyroid levels. Examples include Prozac, Zoloft, and Celexa.

Antipsychotics like Risperdal and Zyprexa can also cause low thyroid levels. Talk to your doctor if you’re taking one of these drugs.


Steroid medications are used to treat asthma, arthritis, and other inflammatory diseases.

They can also be used to prevent rejection after transplantation. Unfortunately, steroids can cause low thyroid levels as well.

Diabetes Medications

People with diabetes may take insulin or oral medications called sulfonylureas. Both of these medications can cause low thyroid levels if taken long-term.

Other Medications

Some other drugs can cause low thyroid levels including antihistamines such as Benadryl, certain antibiotics (such as Flagyl), and some chemotherapy agents.

How Do I Know If My Drug May Be Causing Low Thyroid Levels?

If you’ve been diagnosed with low thyroid levels, talk to your doctor. Your doctor can test your thyroid levels before starting any new medication. 

You’ll need to monitor your thyroid levels while taking the drug. You may need to adjust the dose or stop taking the drug altogether.

If you suspect that your drug might be causing low thyroid levels, talk with your doctor. He or she will help you figure out what’s going on.

Can Recreational Drugs Affect The Thyroid?

What Drugs Affect Thyroid Function?

Yes. Some illegal drugs can temporarily increase or decrease thyroid activity. Examples include ecstasy, cocaine, and marijuana.

The effects of illegal drugs on the thyroid depend on how much of a particular drug is in your system at the time. 

A person who takes a small amount of a drug for several days won’t notice any changes.

But someone who uses large amounts of a drug over a short period of time could experience serious side effects.

What Are Serum TSH Levels?

Serum TSH levels measure the level of thyroid-stimulating hormone in the bloodstream. It’s a simple way to check whether your thyroid is working normally.

TSH levels should stay between 0.4 mIU/mL and 4.0 mIU/mL. Anything outside this range indicates that something is wrong with your thyroid.

Drugs That Suppress Serum TSH Levels

Certain prescription drugs can suppress serum TSH levels. This means that your thyroid produces less thyroid hormone than normal.

Examples of drugs that can suppress TSH levels include:

• Amiodarone

• Carbimazole

• Chlorothiazide

• Clofibrate

• Corticosteroids

• Cyclosporine

• Digoxin

• Diltiazem

• Estrogens

• Fluoxetine

• Hydrochlorothiazide

• Hydrocortisone

• Methotrexate

• Methyltestosterone

• Nifedipine

• Phenytoin

• Prednisone

• Quinidine

• Sulfonamides

• Thiabendazole

• Tricyclics

Symptoms Of Thyroid Conditions

There are many symptoms of a thyroid condition, although some people often don’t realize they have a problem until their thyroid doesn’t work properly.

Symptoms vary depending on which part of the body isn’t functioning correctly.

Here are some common signs of thyroid problems:

  • Fatigue
  • Weight gain
  • Poor memory
  • Muscle cramps
  • Depression
  • Aches and pains
  • Dizziness
  • Headaches
  • Hair loss

Testing For Thyroid Conditions

Your doctor will do tests to check your thyroid level. Tests include:

Blood Test 

This measures levels of TSH, T4, and free thyroxine. It’s important to have this test done regularly because it shows whether your thyroid is working properly.

Serum Free T3 Test 

This test checks how active your thyroid cells are. It’s usually done when there’s a problem with the thyroid gland.

Thyroid Scan 

This test uses radioactive iodine to show where the thyroid gland is located within the neck.

Thyroid Ultrasound 

This test uses sound waves to look at the size and shape of the thyroid gland.

Treatment Options For Thyroid Problems

There are many options available for treating low thyroid levels. Treatment depends on the cause of the condition.


Low thyroid levels caused by an underactive thyroid gland can often be treated with thyroid hormone replacement therapy.

Your doctor will prescribe a medicine that contains synthetic versions of the hormones found naturally in the body. These medicines are safe and effective.


In rare cases, surgery may be needed to remove part of the thyroid gland. This treatment is only recommended if the thyroid gland is enlarged and has become cancerous.

Radioactive Therapy

Radiation treatments use high-energy rays to destroy abnormal tissue. They’re used to treat cancers of the head and neck, thyroid, breast, prostate, and lung.

Radiation therapy is not always successful. Talk to your doctor about other treatment options.

What Are Thyroid Nodules And Cysts?

Nodules and cysts are growths that occur inside the thyroid gland. Most nodules don’t require medical attention.

However, some types of nodules can cause problems such as pain or difficulty swallowing.

Nodules and cysts can form in the thyroid gland after exposure to radiation during certain diagnostic procedures. In most cases, they aren’t dangerous.


The thyroid gland produces two key hormones that regulate metabolism. When the thyroid gland isn’t producing enough hormones, you’ll experience several symptoms.

The best way to diagnose thyroid conditions is through testing. Some drugs can also help restore normal thyroid function, however, others can interfere with it. 

There are many different ways to treat thyroid problems. If you’ve been diagnosed with hypothyroidism, talk to your doctor about your treatment options.

Tom Anderson
+1 844-569-1713