What’s the Difference Between Hypothyroidism and Hyperthyroidism?

If you have some form of thyroid disease, you’re not alone. Thyroid disease affects about 20 million people in the U.S. There are two common types of thyroid disorders: hyperthyroidism and hypothyroidism. Both can happen if your thyroid gland isn’t working normally. But they’re very different conditions. Let’s take a closer look at hypothyroidism versus hyperthyroidism and how you can tell the difference. 

What is the thyroid?

The thyroid is a gland in the front of your neck. It’s part of the endocrine system, which controls the hormones in your body. Thyroid hormones help you metabolize fats, proteins, and carbohydrates so you can use them for energy. These hormones also help maintain your blood pressure, body temperature, and heart rate.

When your thyroid isn’t working like it should, you may have some form of thyroid disease. There are two main types of thyroid disease: hypothyroidism and hyperthyroidism. 

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What’s the difference between hyperthyroidism and hypothyroidism?

Hyperthyroidism is when you have an overactive thyroid — it makes too much thyroid hormone. Hypothyroidism is when you have an underactive thyroid — it does not make enough. 

These two conditions often have different causes and symptoms. But sometimes the symptoms overlap. For example, a goiter (enlargement of the thyroid) can happen in both types of thyroid disease. 

Symptoms of hyperthyroidism

Common signs and symptoms of hyperthyroidism include:

• Hand tremor

• Weight loss

• Nervousness

• Fast heart rate

• Trouble sleeping

• Brittle skin

• Muscle weakness

• Irritability

• Weaker or less frequent periods

Graves’ disease is the most common cause of hyperthyroidism. It’s an autoimmune disease. This means your immune system sees the thyroid as something foreign and attacks it. This causes the thyroid to grow and release too much hormone. Some people with Graves’ disease also have bulging eyes. This happens because the tissues around them swell.

Other causes of hyperthyroidism include:

• Small masses within the thyroid (toxic nodular goiter) 

• Thyroiditis (inflammation of the thyroid due to a virus)

• Postpartum thyroiditis (after giving birth)

• Intake of too much thyroid hormone

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Symptoms of hypothyroidism

Common signs and symptoms of hypothyroidism include:

• Constipation

• Fatigue

• Cold sensitivity

• Weight gain

• Dry skin

• Forgetfulness

Hypothyroidism occurs when your thyroid is no longer working as well as it should. Or it may happen if your thyroid is removed or destroyed for medical reasons (such as cancer). Hashimoto’s thyroiditis is another autoimmune disease. It’s the most common cause of hypothyroidism in the U.S. 

Other causes of hypothyroidism include:

• Previous radioiodine or surgical treatment of the thyroid  

• Previous radiation for head and neck cancer

• Conditions that affect the pituitary gland in the brain (such as Sheehan’s syndrome)

• Congenital hypothyroidism (present at birth) 

• Medications (like amiodarone and lithium)

How do you diagnose thyroid problems?

Symptoms tend to prompt people with thyroid disease to see their provider. A physical exam and lab tests will then help your provider make the diagnosis of thyroid disease. 

A blood test for thyroid stimulating hormone (TSH) is the best screening test for thyroid problems. TSH is high when your body is not making enough thyroid hormone (hypothyroidism). It’s low when you’re making too much thyroid hormone (hyperthyroidism). 

Your provider may also use blood tests to look for thyroid antibodies and diagnose thyroid disease. Your body may produce certain antibodies in Hashimoto’s thyroiditis or Graves’ disease. These tests can sometimes help to give some clues as to the cause of your thyroid disease. 

Depending on what your lab tests show, your provider may want to get a thyroid ultrasound. This can also help diagnose any thyroid problems you may have.

Is hypothyroidism or hyperthyroidism more dangerous?

Neither condition is more dangerous than the other. Both hypothyroidism and hyperthyroidism can lead to serious complications if left untreated. And both conditions can be life-threatening in severe cases.

If left untreated, hyperthyroidism can lead to serious health issues, like:

• Heart problems

• Vision loss

• Osteoporosis

• Fertility issues

• Pregnancy complications

• Thyroid storm (a life-threatening condition caused by overactive body systems)  

Untreated hypothyroidism can cause serious complications, including:

• Heart disease

• Mental health conditions (like depression and dementia)

• Nerve damage

• Fertility issues

• Pregnancy complications

• Myxedema coma (a life-threatening condition caused by underactive body systems)

How do you treat hyperthyroidism and hypothyroidism? 

Thyroid diseases have different treatments. This is often based on what caused your thyroid function to become abnormal. Let’s review common treatments for hyperthyroidism and hypothyroidism.

Hyperthyroidism treatment

Hyperthyroidism treatment often starts with addressing your symptoms. Beta blockers, like propranolol and atenolol, are commonly prescribed to help with symptoms. These medications help to:

• Slow heart rate

• Decrease tremors 

• Reduce jittery feelings

• Lower blood pressure 

Other treatments for hyperthyroidism decrease thyroid hormone production. This includes: 

• Medications: like methimazole and propylthiouracil

• Thyroid gland destruction: destroying the thyroid cells with radioactive iodine

• Thyroidectomy: removing the gland with surgery

Hypothyroidism treatment

Hypothyroidism is usually treated with thyroid hormone replacement. Levothyroxine is the synthetic (human-made) thyroid hormone most commonly used. In fact, levothyroxine is one of the most prescribed medications in the U.S. 

Your provider will typically select your levothyroxine dose based on your weight. Then you’ll monitor your TSH levels from time to time to see if you need to adjust your dose. The goal is to get your TSH back in the normal range. 

Are hyperthyroidism and hypothyroidism permanent?

Not always. Hyperthyroidism and hypothyroidism are not necessarily permanent, but it depends on the cause. There are some reversible causes of thyroid disease that can improve on their own or once the underlying issue is treated. These include thyroid disease due to: 

• Autoimmune conditions

• Pregnancy

• Medications 

• Too much or too little iodine intake

Hyperthyroidism treatment may involve removing your thyroid (thyroidectomy) or destroying the thyroid tissue. This can cure hyperthyroidism. But as a result, you’re likely to develop lifelong hypothyroidism.

Many cases of hypothyroidism are unlikely to go away. This means you’ll probably need to take medication for the rest of your life. But everyone is different, so talk with your provider about what to expect.

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Written by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined her interests in clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

Edited by:

Karla Robinson, MD

Karla Robinson, MD, is a medical editor for GoodRx. She is a licensed, board-certified family physician with almost 20 years of experience in health through varied clinical, administrative, and educational roles.

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