Should You Get Tested for Hypothyroidism?
Key takeaways:
Thyroid function testing is done with blood tests that measure hormone levels in the body.
You should have testing for your thyroid if you’re having symptoms of hypothyroidism and you’re at risk for the condition.
Experts don’t recommend hypothyroidism screening for everyone. This is because it can easily lead to false diagnosis and unnecessary treatment.
Many people wonder if their thyroid function is low and if they should have it tested. But hypothyroidism is actually less common than it may seem. Less than 5% of the U.S. population has low thyroid hormone levels on a blood test. And more importantly, only 0.3% of people in the U.S. actually have signs and symptoms of low thyroid hormone.
For this reason, the U.S. Preventive Services Task Force doesn’t recommend routine thyroid function screening in healthy adults. That’s because there are no long-term health benefits to diagnosing hypothyroidism before it causes symptoms. And what’s more, it could lead to harm — like an incorrect diagnosis or medication you don’t need.
But if you’re experiencing symptoms that could be due to hypothyroidism — and you’re at higher risk for the condition — you may need testing. So we’ll review how to know if you need testing for your thyroid.
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What is hypothyroidism?
Hypothyroidism is a condition where your body has lower than normal levels of thyroid hormones. Thyroid hormones affect many different parts of the body. They play an important role in metabolism, mood, growth, and development. Because of this, the symptoms of hypothyroidism can affect almost every part of your health.
The main causes of hypothyroidism are:
An autoimmune condition called Hashimoto’s thyroiditis
Specific medications and treatments (mainly ones that treat hyperthyroidism)
How do you test for hypothyroidism?
Testing for hypothyroidism is done with thyroid function tests. Usually you can do these at a laboratory or your primary care provider’s office. Depending on your particular history and risk factors, you may need some or all of the following tests:
Thyroid stimulating hormone (TSH)
Free thyroxine (free T4)
Total thyroxine (total T4)
Free triiodothyronine (free T3)
Total triiodothyronine (total T3)
Anti-thyroperoxidase (anti-TPO) antibodies
TSH test
If your primary care provider suspects that you need thyroid testing, then the best screening test is a TSH test. TSH is a signal hormone that the brain sends to the thyroid to encourage it to ramp up, maintain, or slow down thyroid hormone production.
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Your TSH can either be low or high, depending on the type of hypothyroidism you have. TSH will be high in most people with hypothyroidism.
T4 test
Thyroxine (T4) is the main form of thyroid hormone in the blood. This is usually measured by something called free T4. In hypothyroidism, free T4 levels are generally low. Your primary care provider may decide to measure the total T4 as well as free T4 if they’re concerned about a specific type of hypothyroidism.
T3 test
Triiodothyronine (T3) is the active form of thyroid hormone. T3 levels are also low in hypothyroidism. About 80% of the T3 in the body is made from T4. The liver and kidneys can turn T4 into T3, which the body then uses.
Anti-TPO antibodies
Hashimoto’s thyroiditis is a specific kind of hypothyroidism. People with Hashimoto’s thyroiditis often end up with hypothyroidism because they have certain antibodies (anti-thyroperoxidase, or anti-TPO antibodies) that destroy thyroid cells. If your primary care provider suspects you have this condition, they may add a test for anti-TPO antibodies to your other thyroid tests.
Normal thyroid levels
Each laboratory has a slightly different range of normal thyroid hormone values. But, in general, thyroid tests are considered to be normal if they’re within these ranges:
TSH: 0.4 mIU/mL to 4.5 mIU/mL
Total T4: 4.5 ug/dL to 12.5 ug/dL
Free T4: 0.8 ng/dL to 2.0 ng/dL
Total T3: 80 ng/dL to 215 ng/dL
Free T4: 1.5 pg/mL to 6.0 pg/mL
TPO Ab: Less than 34 IU/mL
Even if your levels fall within these ranges, it’s still a good idea to discuss your test results with a knowledgeable healthcare professional. They can help you interpret your results in the context of your symptoms and any previous test results.
What are the symptoms of hypothyroidism, and who should get tested?
You should get your thyroid tested if you have symptoms of hypothyroidism and you’re in a high-risk group (details below).
Symptoms of hypothyroidism can sometimes be hard to identify. They can be subtle. And many other health conditions can cause the same symptoms. Hypothyroidism symptoms include:
Cold intolerance (feeling cold when others are not)
Brittle nails
Muscle aches
Poor concentration or memory
Enlarged thyroid gland (goiter)
Slowed growth and development (in children)
Difficulty getting pregnant
Since these symptoms are so common — and they are more likely caused by something other than your thyroid — it also helps to know if you are at higher risk for hypothyroidism.
High-risk groups for hypothyroidism
Hypothyroidism can affect anyone, but you may be especially at risk if you:
Are female
Are over age 60
Have low iodine levels (very rare in the U.S.)
Have a family history of thyroid problems
Are taking certain medications that contain iodine (like lithium or amiodarone)
Have had radiation treatment on the head, neck, or chest
Have had thyroid surgery
Are pregnant or have recently been pregnant
You may be wondering why experts don’t recommend screening for hypothyroidism in everyone. First, there’s no evidence that diagnosing hypothyroidism before it causes symptoms has any long-term health benefits. Plus, there are actually some risks:
Your insurance may not cover the cost of your lab test if it’s not clear you need it.
There’s a chance that a “false positive” result could lead to a misdiagnosis and/or treatment that you don’t need. This means you won’t find the true cause of your symptoms. Plus, you may unnecessarily start a medication and develop harmful side effects.
Your thyroid test might reveal subclinical or borderline hypothyroidism. This is when your results are only slightly abnormal. But borderline hypothyroidism often goes away on its own. So treatment may do more harm than good.
Testing for hypothyroidism in pregnancy
Screening for hypothyroidism in pregnancy is an entirely different matter. Hypothyroidism in pregnancy can be dangerous to both the mother and baby. So a healthcare professional may recommend a thyroid screening test even if the mother doesn’t have any symptoms. For example, they may recommend testing if the pregnant woman’s mother has hypothyroidism.
A knowledgeable healthcare professional should perform testing for hypothyroidism during pregnancy because pregnancy hormones can affect thyroid hormone test results. This makes the tests more challenging to interpret.
Frequently asked questions
The main way to test for hypothyroidism is with lab tests for TSH and other thyroid hormones. There are other tests that can help assess thyroid health, like an ultrasound of the thyroid gland. There’s also something called a radioactive iodine uptake test. This is a special type of scan that measures how well the thyroid gland is taking up iodine in the body, which it uses to make thyroid hormone. While this can help diagnose hypothyroidism, it’s not first-line testing and it’s not necessary for most people.
Yes, there are at-home options for thyroid testing. They require a pinprick blood sample, which can then be sent off to a lab. These may be a convenient option for people who wish to screen themselves for hypothyroidism. But if you’re having any symptoms of hypothyroidism, it’s best to see a healthcare professional for formal testing. They can make sure you’re getting the proper testing and can help you interpret the results. They can also evaluate whether your symptoms could be coming from a different medical condition.
The bottom line
Not everyone needs testing for hypothyroidism. And your primary care provider can help you figure out if you need your thyroid function checked. This is most important for people who are at risk for the condition and also have symptoms of hypothyroidism. Otherwise, testing may do more harm than good. It can lead to a false diagnosis and medication you don’t need.
But if you’re concerned about new symptoms or think your thyroid might be off, bring up these concerns with your primary care provider. They’ll work with you to find the cause of the problem — whether it be your thyroid or a different medical condition.
Why trust our experts?
References
American Thyroid Association. (n.d.). Thyroid function tests.
Bekkering, G. E., et al. (2019). Thyroid hormones treatment for subclinical hypothyroidism: A clinical practice guideline. The British Medical Journal.
Gaitonde, D. Y., et al. (2012). Hypothyroidism: An update. American Family Physician.
Hollowell, J. G., et al. (2002). Serum TSH, T(4), and thyroid antibodies in the United States population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). Journal of Clinical Endocrinology and Metabolism.
Labcorp. (n.d.). Thyroid peroxidase (TPO) antibodies.
Stagnaro-Green, A., et al. (2011). Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid.
U.S. Preventive Services Task Force. (2014). Thyroid dysfunction: Screening.
