Healthcare provider examining woman's neck for possible hypothyroidism

How to test for hypothyroidism

Medically reviewed on August 17, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.


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First, you experienced fatigue. Then, you gained weight, had dry skin, and felt pain in your joints and muscles. Concerned, you searched the internet for information. After entering your symptoms into the search bar, hypothyroidism flashed across your screen.

If you think you have hypothyroidism, it’s important to see your healthcare provider as soon as possible.

In the meantime, we’ll fill you in on how to test for hypothyroidism. That way, you can know exactly what to expect—from the first test to the last step in your treatment plan.

What is hypothyroidism?

The thyroid is a powerful part of the endocrine system. In addition to regulating metabolism, thyroid function: [1]

  • Impacts cardiovascular health
  • Enables bone growth
  • Keeps body temperature in check

It does this through the secretion of powerful thyroid hormones—most notably thyroxine.

When the thyroid is properly working, thyroid hormones enable the body to carry out many essential bodily processes. However, sometimes the thyroid produces too little thyroid hormones. The result is a common condition known as hypothyroidism. [2]

Causes

When healthcare providers test for hypothyroidism, they typically look for one of five main causes of underactive thyroid: [2]

  • Primary – In most cases, hypothyroidism is caused by a reduction in the levels of the thyroid hormone thyroxine. This reduction is, in turn, caused by the prevalence of anti-thyroid antibodies that disrupt hormone production.
  • Secondary – Whereas reductions in thyroxine levels cause primary hypothyroidism, reductions in thyroid stimulating hormone (TSH) levels cause secondary hypothyroidism. We’ll unpack TSH later, but for now, know that TSH helps regulate the release of other thyroid hormones.
  • Tertiary – Tertiary hypothyroidism stems from a reduction in the thyroid hormone thyrotropin. Thyrotropin helps stimulate hormone production.
  • Peripheral – Peripheral hypothyroidism, also known as consumptive hypothyroidism, is an exceedingly rare form of the condition. It’s caused by an overproduction of an enzyme that inhibits thyroid hormone production.
  • Central – Central hypothyroidism is marked by low thyroxine and TSH levels. As a result, this form of hypothyroidism blends both primary and secondary causes.

Now that you know the five main causes of hypothyroidism, let’s take a closer look at the hormones typically measured by thyroid and metabolic tests.

Measured hormones

Like a finely-tuned vehicle, the thyroid gland is composed of many components that play important, individual roles. In the case of the thyroid, these components are: [3]

  • Thyroxine – Also known as T4, thyroxine is the main hormone produced by the thyroid. In addition to helping regulate metabolism, thyroxine plays a role in bone growth. However, thyroxine can’t do its work on its own. When thyroxine is secreted into the bloodstream, the body converts it to the “active” hormone triiodothyronine.
  • Triiodothyronine – Also known as T3, healthcare providers consider triiodothyronine the “active” thyroid hormone. That’s because T3 is the only thyroid hormone capable of directly impacting the cells and metabolism.
  • Thyroid stimulating hormone – As stated above, thyroid stimulating hormone, also known as thyrotropin, is responsible for stimulating and monitoring the production of T3 and T4.

In addition to testing for the above hormones, some of the best at-home lab tests even look for thyroid antibodies. These antibodies can inhibit normal thyroid gland functioning.

Types of hypothyroidism tests

Tests are available to measure thyroid hormone levels and help you learn more about the thyroid. Although the thyroid’s inner workings can be complex, modern hypothyroidism tests can be relatively straightforward. These thyroid tests typically consist of the following blood tests: [4]

  • T3 test – T3 tests measure triiodothyronine levels in the bloodstream. Although these tests are more useful in diagnosing hyperthyroidism, T3 blood tests can also detect low levels of triiodothyronine. To fall in the normal range, measured triiodothyronine levels should be between 100 and 200 ng/dL.
  • T4 test – T4 tests measure thyroxine levels. The normal range for thyroxine is between 5 and 11 mg/dL.
  • TSH tests – TSH tests measure the levels of thyroid-stimulating hormone levels in the bloodstream. Higher levels from a TSH test may indicate hypothyroidism while lower levels may indicate hyperthyroidism. Normal TSH levels fall between 0.40 and 4.50 mIU/mL.

In addition, some thyroid tests may measure free T3 and T4. Free T3 and T4 tests measure thyroid hormones by separating the hormones from the natural proteins that bind to them. As a result, these tests can provide more accurate results.

Thyroid blood tests can either be performed at home or at a healthcare provider’s office. Let’s take a closer look at both types of tests.

At-home lab tests

If you’re wondering about how to check your thyroid at home, at-home thyroid tests allow you to test thyroid hormone levels from the comfort of your home. Once you take your blood sample, you typically send it to a certified lab or your healthcare provider. Your healthcare provider will then provide you with personalized results and an action plan.

Components

Although the specific components of each test depend on the manufacturer, most thyroid and metabolism tests contain the following test components:

  • Lancet – A lancet is used to prick the finger to draw the blood sample.
  • Alcohol pad – Any dirt, debris, or bacteria on the finger can tarnish the blood sample. As a result, many at-home lab tests contain an alcohol pad to disinfect the collection area.
  • Gauze and bandage – Although the lancet is designed to draw only a small sample of blood, you’ll still need to cover the collection area with gauze and a bandage.
  • Collection card – Many tests contain a collection card. Once you prick the finger, you’ll squeeze a few drops of blood onto the collection card.
  • Biohazard bag – Even though the test requires a small blood sample, any amount of blood can pose a biohazard risk. Once you collect a sample, you’ll place the collection card in the biohazard bag.
  • Prepaid return shipping label – Many at-home lab test kits make the process easier by providing a prepaid return shipping label. That way, you can easily send the sample where it needs to go.

Once you’ve gathered the testing components, it’s time to take your at-home lab test.

Testing procedures

Whether you’re taking a thyroid test, you’ll need to take the following steps:

  1. Register the test (if applicable). Many at-home lab tests allow you to register the test with the testing company. That way, you can receive quick, personalized results delivered right to your smartphone or computer.
  2. Wash your hands and disinfect the testing area. Convenience is one of the main benefits of at-home lab tests. You can test from anywhere. That said, many people choose to collect their samples in their bathrooms. That’s because you’ll need to wash your hands with soap and warm water. You’ll also need to disinfect the collection area with the alcohol pad.
  3. Collect the sample. Using the lancet, prick your finger and gently squeeze a few drops of blood onto the collection card. Make sure the sample soaks through the collection card.
  4. Place the collection card into the biohazard bag. Place the biohazard bag into the envelope with the prepaid return shipping label.
  5. Wash your hands and clean the area. During the collection process, you might have accidentally squeezed a few drops of blood outside of the collection area. Make sure the collection area is clean and disinfected.
  6. Wait for the results. Depending on the testing company, results may arrive within a few days.

Many people favor at-home lab tests for their convenience and accessibility. Once you take your at-home lab test, your healthcare provider may schedule you for additional tests.

In-office tests

You may also choose to schedule a thyroid and metabolism test at your healthcare provider’s office. While a healthcare provider will likely perform the standard blood tests, they may also schedule one or more of the following tests: [5]

  • Radioactive iodine uptake test – This test measures how much iodine the thyroid absorbs from the blood to produce hormones. To administer this test, a healthcare provider will have you ingest radioactive iodine. Then, they’ll measure the amount of radioactive iodine the thyroid uses.
  • Ultrasound – Ultrasounds can be effective at detecting potentially cancerous lumps in thyroid nodules. Furthermore, they can map out thyroid nodules to let healthcare providers know if they’re impacting thyroxine levels.
  • Thyroid scan – Similar to a radioactive iodine uptake test, a thyroid scan measures the amount of radioactive iodine the thyroid absorbs from the bloodstream. The amount of absorbed iodine can let healthcare providers know the causes of hypothyroidism.

When it comes to understanding how to balance thyroid hormones, a test is the first step to determining a path for potential treatment.

Everlywell: Thyroid Testing Made Easy

An imbalance in thyroid hormone levels can cause a few conditions, including an overactive thyroid and an underactive thyroid gland, impacting thyroid health function. Thyroid testing is a key step towards understanding how well-balanced your thyroid hormone levels are.

With the Everlywell at-home Thyroid Test, all you need to do is collect your sample and send it to a CLIA-certified lab partner. Within a few days, you’ll receive results and helpful information on potential next steps.

How to Balance Thyroid Hormones

How to Check Thyroid at Home: 3 Methods

Are Thyroid Problems Genetic?


References

  1. StatPearls. Physiology, Thyroid Hormone. URL. Accessed August 17, 2022.
  2. Lancet. Hypothyroidism. URL. Accessed August 17, 2022.
  3. Cleveland Clinic. Thyroid Hormone. URL. Accessed August 17, 2022.
  4. Cleveland Clinic. Thyroid Blood Tests. URL. Accessed August 17, 2022.
  5. National Institute of Diabetes and Digestive and Kidney Diseases. Thyroid Tests. URL. Accessed August 17, 2022.
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