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The Best At Home Thyroid Test

Everything you need to know about taking a thyroid test at home.

Last Updated: Nov 23, 2021

Thyroid Test At Home

Problems with thyroid health are all too common. Up to 60% of the 20 million Americans estimated to have some thyroid condition are unaware they have the disease. Thyroid conditions are particularly prevalent among women, with one in eight likely to develop a disorder in their lifetime. It’s essential to learn if your thyroid is not functioning correctly as soon as possible and to re-check routinely.

A handful of companies have perfected the ability to deliver state-of-the-art thyroid test kits to your home and evaluate your sample with outstanding accuracy. We’ve tested these companies and their products to help you determine which at-home thyroid test will be best for you.

Read on for all the details, but for those in a hurry, here is a summary of our main findings:

What is the best at home thyroid test?

Summary of our recommendations

Our Top Choice

LetsGetChecked

Both of the LetsGetChecked at-home thyroid tests are highly recommended and our picks for best value.

LetsGetChecked is a respected at-home testing company that receives high ratings in terms of price, accuracy, privacy, and customer support.

Current Deals: Save 30% with coupon code: INNERBODY30

How we evaluated at home thyroid tests

Cost

Winner: LetsGetChecked

Our evaluation of cost had a lot more to do with value than who had the lowest price. Technically, the least expensive thyroid test comes from Healthlabs, but it pales compared to its competitors in terms of thoroughness and convenience. And while the LetsGetChecked test is about $20 more than similar tests by Paloma Health and Everlywell, its measurement of thyroglobulin antibodies (instead of just thyroid peroxidase antibodies) makes it the best value in the bunch.

Here’s a quick breakdown of basic costs:

  Cost Cost with Innerbody Promotion Total Biomarkers Tested
LetsGetChecked Thyroid $99 $69 4
LetsGetChecked Thyroid Antibody $119 $83 6
Healthlabs Thyroid Panel with TSH $59 N/A 3
Everlywell Thyroid $99 $84 4
myLAB Box Thyroid $139 $111 4
Paloma Health Complete Thyroid $99 $74 4

Speed

Winner: LetsGetChecked

Our speed rating included everything from shipping and test turnaround time to the time it takes to navigate a website for purchases and answers to common questions. At every turn, LetsGetChecked excels, with an intuitively laid out website and a turnaround that, for our testers, took just eight days from the day we placed the order to the day we had results.

Customer care

Winner: LetsGetChecked

LetsGetChecked also comes out on top for customer care. Their email responses are quick and thorough, and the people in their phone banks have enough information about tests and processes that they rarely need to run questions up the chain to get you an answer. And their convictions run deep. On the STD side, they even offer free delivery of free medications after specific positive test results. In short, they go above and beyond the rest.

Accuracy

Winner: Four-way tie

The four at-home services we review here utilize blood spot immunoassay testing that boasts an incredibly high degree of accuracy. Collection methods and sample processing are nearly identical, but we excluded the Healthlabs test from this group of winners for a specific reason. As you’ll read below, Healthlabs can test with accuracy equal to their competitors, but only if you purchase additional tests dedicated to specific biomarkers that the other companies test for by default.

Why you should trust us

At Innerbody Research, we extensively test each health service we review, including these thyroid testing services. All told, our team has spent over 83 hours testing and researching the thyroid test kits and related services of these companies to provide an accurate, unbiased analysis of how the products and services compare, free of marketing jargon and gimmicks.

Over the past two decades, Innerbody Research has helped tens of millions of readers make more informed decisions to live healthier lifestyles. We evaluate the service based on adherence to quality, the latest medical evidence and health standards, and a simple question: would we buy the product or service ourselves if it weren’t part of our job, and would we recommend it to family and friends?

Additionally, like all health-related content on this website, this review was thoroughly vetted by one or more members of our Medical Review Board for accuracy.

Should you get a thyroid test?

LetsGetChecked Thyroid test guide kit

Getting your thyroid function tested is a good idea no matter who you are, but some populations are statistically at higher risk of developing thyroid conditions:

  • Women
  • Type 1 diabetics and those with other autoimmune disorders
  • New mothers
  • People who smoke
  • Those with a family history of thyroid disorders
  • People who have symptoms of hypothyroidism or hyperthyroidism

Women are around five to eight times more likely to have thyroid problems, with one in eight women developing thyroid disease during their lifetime.

Since thyroid issues are common, periodic testing is an excellent idea regardless of whether you are experiencing any symptoms of thyroid dysfunction.

Get a Thyroid Test

Symptoms of thyroid disease

Located below the larynx at the front of the neck, the thyroid is a small gland with two lobes connected by a bridge of tissue. Although not very large, the butterfly-shaped thyroid gland plays a significant role in ensuring the proper function of the brain, heart, kidneys, liver, metabolism, and skin.

Conditions arise when the thyroid is either overactive in its hormone production or underactive and produces too little. Overactive thyroid glands create a condition called hyperthyroidism, while an underactive thyroid gland results in hypothyroidism. Problems with the thyroid usually result in the overproduction or underproduction of thyroid hormones.

The overproduction of thyroid hormones, known as hyperthyroidism, can be caused by conditions such as:

  • Graves’ disease (an autoimmune disease and the most common cause of hyperthyroidism)
  • Toxic adenomas (nodules developing in the gland which secrete extra thyroid hormones)
  • Subacute thyroiditis (inflammation of the thyroid that results in the leaking of extra hormones)
  • Dysfunction of the pituitary gland, which regulates the action of the thyroid, causing excess production of thyroid hormones

Hypothyroidism is the underproduction of thyroid hormones. This can be caused by:

  • Hashimoto’s thyroiditis (an autoimmune disorder)
  • Exposure to toxic levels of iodine

Common symptoms of hypothyroidism include:

  • Lethargy
  • Gaining weight without eating more
  • Muscle pain or weakness
  • Digestion issues like constipation
  • Foggy memory
  • Feeling unusually chilly
  • Concentration difficulties
  • Depression
  • Skin or hair dryness
  • Bradycardia (slow heart rate)
  • Frequent or heavy periods

Common symptoms of hyperthyroidism include:

  • Rapid heart rate
  • Irregular heartbeat
  • Losing weight
  • Feeling overheated
  • Sweating more
  • Increased hunger
  • Frequent bowel movements
  • Anxiety and heightened nervousness
  • Shaky, trembling hands
  • Sleep problems and disturbance
  • Weakened skin, nails, and hair
  • Irritability
  • Muscle weakness
  • Missed or light menstrual periods

Should you test at home or in person?

Whether you test at home or in person at a lab depends mainly on your personal preference, but if you’re not sure which method would be best for you, we’ve put together a little chart to help you.

  Test at Home Test in Person
Limited time to spare
Yes
 
Squeamish about blood  
Yes
Squeamish about needles
Yes
 
Need results fast  
Yes
Limited transportation
Yes
 
Poor circulation  
Yes

Of course, there are other reasons someone might want to test at home or in person, but we think the convenience of the at-home testing experience is one of the most exciting things happening in modern medicine.

Here’s a handy chart comparing each company’s most comprehensive test choices based on price and what the tests measure.

  LetsGetChecked Thyroid Antibody Test Healthlabs Thyroid Panel w/ TSH Everlywell Thyroid Test myLAB Box Thyroid Health Test Paloma Health Complete Thyroid Test
Price $119 $59 $99 $139 $99
TSH
Yes
Yes
Yes
Yes
Yes
Free T4
Yes
Yes
Yes
Yes
Yes
T3
Yes
 
Yes
Yes
Yes
TPO/TPEX
Yes
 
Yes
Yes
Yes
T4
Yes
Yes
     
Thyroglobulin Antibodies
Yes
       

Thyroid testing FAQ

Are home thyroid tests reliable?

At-home thyroid tests are reliable and accurate. The top testing companies, including all of the companies we compare in this guide, partner only with certified labs of the caliber that health centers use for analysis. For thyroid testing, these companies rely on proven blood drop sample assays to deliver accurate results.

The instructions for this kind of test are straightforward, and your kit will include all of the information and materials you’ll need to administer it correctly.

As long as you follow the instructions in your at-home test kit, your lab tests should be as accurate as if you had a test administered in an office setting.

Do I need to fast before a thyroid test?

To get the most accurate possible picture of your thyroid health, you should not fast leading up to the test. TSH levels and other thyroid indicators fluctuate naturally throughout the day, but fasting can elevate TSH levels. Unless you perform the same fast daily, a fasted thyroid test will provide an inaccurate picture of your thyroid function.

Other factors that can impact the accuracy of your test include:

  • Medication - Don’t stop taking prescription medications for the sake of your test, but if you get an abnormal result, share the results and your medication status with your physician.
  • Illness - If possible, avoid taking a thyroid test while sick (unless you suspect your symptoms to be thyroid-related). Even something as simple as diarrhea can affect your results.
  • Pregnancy - This is also not a reason to avoid a test, but it may help explain an abnormal result, as levels fluctuate dramatically during pregnancy.

What are early warning signs of thyroid problems?

Hyperthyroidism and hypothyroidism often create opposite effects in the body, making it difficult to determine whether you have a thyroid problem without testing. There are early warning signs of either condition — as well as other potential thyroid problems — that should warrant a test, especially when it’s as easy to test now as it has ever been.

  • Elevated heart rate - An overworked thyroid gland can cause an escalation in heart rate and blood pressure.
  • Excessive fatigue - An underactive thyroid can have the opposite effect, causing deep and consistent tiredness.
  • Fluctuations in weight - Depending on whether you have hyper- or hypothyroidism, you may lose or gain weight without an apparent cause.
  • Inconsistent body temperature - Your metabolism is crucial in regulating body temperature, and a thyroid problem can make you feel unusually hot or cold.
  • Problems sleeping - This can result from either hyper- or hypothyroidism, depending on how your activity levels influence your energy at the end of the day.
  • Brain fog - Trouble concentrating or remembering simple details can indicate issues with thyroid health.

These are just a few of the many warning signs related to thyroid health. Anything that makes you think you might have a thyroid problem is a good reason to get tested since you have nothing to lose by learning whether your thyroid is part of the problem.

Do thyroid problems happen suddenly or gradually?

Symptoms related to thyroid disorders can take several months or even years to develop. You might live with a thyroid disorder for a long while before connecting it with a symptom like brain fog. Because some thyroid issues relate to autoimmune diseases or certain cancers, getting tested is vital.

How do I interpret my thyroid test results?

The interpretation of thyroid blood tests can also be problematic. Reference ranges determine low, normal, or high levels of thyroid hormones. Many test reports will display your results next to a numerical representation of these ranges so you can see whether it falls safely within them. We particularly appreciate Everlywell here, as they show you a visual representation of the range with your measurement plotted on it.

That way, you can see how close to the high or low end of a typical range your results lie. That makes it a lot easier to visualize your thyroid health than a number like 3.3 pg/mL.

While these ranges are based on many studies, what is normal to the population is not necessarily typical to the individual. Each person has a different hormonal and chemical composition, and deviations from regular references may be normal for the individual.

Additionally, because these references arise from statistics and averages, the closer the test results are to either the lower or higher limit, the greater the uncertainty of whether the patient has thyroid disease. Likewise, if results are within the reference range but close to the limits, symptoms may still be present.

For these reasons, you should see blood tests as one portion of a diagnosis that includes symptoms, medical history, a physical examination, and imaging (e.g., ultrasound of the thyroid gland).

What happens if test results indicate a thyroid problem?

If any of your results come back abnormal, it’s important to remember that this is not a diagnosis. Before looking into at-home thyroid remedies, you should take your results to your doctor.

Many at-home test providers have nurses or doctors on staff to talk to for free when you post an abnormal result. This is an excellent service for the uninsured, but if you have a regular physician, you should take your results to them.

Your doctor will likely retest those parameters and order additional tests, perform a physical examination, and go over your medical history to determine whether factors other than a thyroid disorder could have influenced your results. From there, the two of you can figure out a treatment plan.

LetsGetChecked thyroid testing

LetsGetChecked is currently our top recommendation for an at-home thyroid test. They offer two testing levels, the most comprehensive of which is the only test in this review to look for thyroglobulin antibodies. They boast exceptional speed in both shipping and lab work, and their customer service staff is among the most knowledgeable out there.

  • Partners with lab facilities that are CLIA-, INAB-, CPA-, or CAP-certified
  • Free phone consultation with a registered nurse if you test positive for specific medical conditions
  • Live online chat to answer pre-purchase questions
  • Innerbody Research readers can save 30% by using the promo code: INNERBODY30

Best for most people: Thyroid Test

The LetsGetChecked Thyroid Test ($99) evaluates thyroid function via analysis of three biomarkers:

  • Thyroid-stimulating hormone (TSH)
  • Free triiodothyronine (FT3)
  • Free thyroxine (FT4)

This test is ideal for most people because it can effectively indicate whether you have an underlying thyroid disorder. Unless you are symptomatic or have other reasons to suspect that you have a particular thyroid disorder (due to family history, radiation exposure, etc.), we recommend this test as the first step in checking your thyroid health. It tests the three primary values related to thyroid function; these serve as the solid starting point to identify whether there is likely a thyroid problem.

Best comprehensive test: Thyroid Antibody Test

The more comprehensive Thyroid Antibody Test ($119) includes analysis of the same three biomarkers as the smaller Thyroid Test, in addition to two more:

  • Thyroglobulin antibodies (TgAb)
  • Thyroid peroxidase antibodies (TPO/TPEX)

The main difference between the two kits is that the TgAb and TPEX values included in the Thyroid Antibody Test can indicate whether thyroid dysfunction is related to an autoimmune disorder. The basic Thyroid Test kit can indicate if there may be an issue with your thyroid, but the more comprehensive test provides insights into the underlying cause.

LetsGetChecked offers a litany of practical at-home tests that cover everything from STDs to celiac disease. To learn more about them, visit our full LetsGetChecked review.

HealthLabs: our top choice for in-lab thyroid tests

Some people would prefer to test in a controlled lab setting and not administer a test themselves. HealthLabs provides an excellent array of in-lab thyroid tests. They are easily our top recommendation for in-lab thyroid testing because:

  • You can order your test conveniently from home.
  • There’s no appointment necessary.
  • With over 4,500 lab locations nationwide, most people find a very convenient lab location near them.
  • Labs are high-quality — the same labs that analyze tests from doctors’ offices, and the same testing methodology.
  • Because of the possibility of same-day testing, you can have results within just 2-3 days of ordering the test.
  • HealthLabs’ thyroid testing options include thyroid panels and single-measurement tests, all of which are reasonably priced.

Visit Healthlabs

One downside to the structure of their thyroid testing is that their most comprehensive testing panel doesn’t test for free T3. Rather, it calculates the value by inserting T4 and the overall thyroxine-binding globulin in the blood into an equation. If you want to get a more accurate measurement of T3, you’ll have to use the company’s more expensive T3 test. You can learn more at our full HealthLabs review.

Everlywell’s Thyroid Test

Based on our comprehensive testing of major testing companies, we consider Everlywell to be a top-notch provider and recommend them over other companies for several tests. But in the case of at-home thyroid testing, LetsGetChecked is still superior.

Everlywell’s popular Thyroid Test ($99) evaluates thyroid function by analyzing four measurements:

  • Thyroid-stimulating hormone (TSH)
  • TPO (a thyroid antibody)
  • T3
  • T4

There is one instance in which this test becomes a better value than the test from LetsGetChecked. Everlywell now offers a membership program that costs $24.99 each month. Members can purchase one qualifying test per month at the guaranteed price of $24.99, as well. So, you could sign up for a monthly membership with everlywell, and if you make the thyroid test one of your monthly choices, you would theoretically be getting it for under $50.

Since LetsGetChecked offers a more comprehensive test without a membership prerequisite for savings, they remain a better choice for at-home thyroid testing.

Like many of the companies in this guide, Everlywell offers more than just thyroid testing. To learn more about Everlywell and their membership program, check out our full Everlywell review.

Paloma Health's Thyroid Blood Test Kit

Paloma Thyroid test kit

Paloma Health is a telemedicine company with a laser focus on thyroid health. In some ways, that specialty purpose gives them an edge over the competition in thyroid matters. Unfortunately, it’s not quite enough for us to recommend them over some others.

One issue is that Paloma’s services are only available in a limited number of states. Specifically, they can provide test kits to every state except for:

  • New York
  • New Jersey
  • Rhode Island
  • Maryland

Doctor consultations are even less accessible than test kits. Currently, Paloma Health can offer consultations in the following states:

  • Arizona
  • California
  • Colorado
  • Florida
  • Illinois
  • Indiana
  • Maryland
  • Minnesota
  • Montana
  • Missouri
  • Ohio
  • Pennsylvania
  • Tennessee
  • Texas
  • Virginia

If you don’t live in one of these 15 states, you cannot get a doctor’s consultation through Paloma. Telemedicine is a highly regulated industry, but they seem to have a more challenging time broadening their reach than others. They also suffer from slower shipping and processing times, which can be a source of frustration.

Still, their customer service is excellent, and they’re the only provider we know of that includes a giant butterfly-shaped lollipop in every test kit.

Visit Paloma

So, with time and effort, they stand to become a serious player. In the meantime, you can learn more about Paloma, as well as their currently limited (but promising) thyroid medical and nutritional consultations, by checking out our full Paloma Health review.

myLAB Box Thyroid Health Screening Test

One of the things that sets myLAB Box apart from their competition is how they bundle their wide variety of tests. You can use their services to check for everything from food sensitivities to sexually transmitted infections. Still, targeted bundles like their Sleep and Stress Test or Anti-Aging Test are among their most attractive.

myLAB Box offers a standalone thyroid test that measures TSH, T3, T4, and TPO. They aren’t our top recommendation for cost reasons, as competitors offer similar tests for a little less. Some of myLAB Box’s other tests measure TSH, T3, or T4 as part of a larger picture of your health. If your thyroid investigation has more to do with a particular problem — like weight control or aging, some of these bundles might be worth your while. Here’s a breakdown of the various myLAB Box tests that feature thyroid biomarkers:

Thyroid Screening Test

This is myLAB Box’s standalone thyroid test. Requiring a simple finger prick blood sample, it measures levels of TSH, T3, T4, and TPO antibodies.

Weight Loss Test

The Weight Loss Test is a pretty comprehensive panel that measures TSH along with estradiol, testosterone, progesterone, DHEA, cortisol, HbA1c, high sensitivity C-reactive protein (hsCRP), and vitamin D levels. These factors — hormones, blood sugar, vitamin D — help paint a picture of your current weight situation and your potential to make any needed adjustments. However, its thoroughness comes at the hefty cost of $239, and it requires a blood sample and a saliva sample.

Metabolism Test

The Metabolism Test is a stripped-down version of the Weight Loss Test, with measurements for TSH, cortisol, and testosterone. While not a complete picture, this is enough information to identify whether your metabolism may run faster or slower than you think. It costs $99 and requires both blood and saliva.

Skin Vitality Test

Another panel focusing on hormonal balance, the Skin Vitality Test measures biomarkers associated with the skin’s susceptibility to wrinkles, fine lines, and liver spots. It requires blood and saliva samples and costs $209.

Anti-Aging Test

The Anti-Aging Test is a ramped-up version of the Skin Vitality Test, looking for all the same biomarkers in addition to fT3, fT4, TSH, cholesterol, and triglycerides. At a price of $219, this deeper dive includes measurements you can potentially address with dietary and lifestyle changes to forestall the aging process. It requires blood and saliva.

Fitness Test

Ideal for those looking to maximize their efforts at the gym, the Fitness Test measures testosterone, DHEA, cortisol, TSH, hsCRP, and vitamin D.

What to expect from the testing process?

The most significant difference among these tests is the difference between the Healthlab in-person screening and the at-home sample collection that every other test uses. Let’s take a look at both with a little more detail.

Testing in a lab

When you place your order with Healthlabs, you’ll have the opportunity to select a lab in your area. In more populated areas, you may have several labs to choose from. If Healthlabs recommends a lab that’s a little farther away than the one you initially selected, we suggest you make the switch. Healthlabs contracts with thousands of labs throughout the US, and some are a lot better than others. Our testers found that out the hard way, so you won’t have to.

Usually, within 30 minutes of your order, you can visit the lab as a walk-in and wait for an opening to have your sample collected. This wait varies significantly, so if your testing needs are not urgent, you may prefer to make an appointment with the lab and go in at an agreed-upon date and time.

The blood draw itself takes just a few moments, and you’ll need to keep a cotton ball taped to the vein for 30 minutes afterward. From that point, all you have to do is wait. Within 48 hours, you’ll receive an email telling you your results are ready, and you can log into your account on the Healthlabs website to view them. A printable PDF is available, and you can call the company to speak with a medical expert if you have any pressing questions about your results.

Testing at home

Testing from home requires a little more patience, as you’ll usually wait 2-5 days for your test kit to arrive in the mail. And if it comes on a Thursday or Friday, you’ll want to wait until Monday to take the test. That’s because weekend postal delays could theoretically be long enough that your sample might become non-viable. It’s a slim chance, especially given the durability of the blood spot tests these companies use, but it isn’t a chance worth taking.

The kit itself will contain instructions, and every kit we mention here asks you to go online and register your test before doing anything else. This is an advisable practice to ensure that you don’t forget to do it later, which would make your sample impossible for the lab to track.

After you register, you can prepare the area you intend to use for your collection. It should be as clean and uncluttered as possible. You’ll then want to wash your hands thoroughly and review the instructions for blood collection.

Most will go like this: Press the lancet into the side of the tip of your least important finger. Try the ring finger on your non-dominant hand. The pinky is often too small to be a reliable source of blood for collection. Make sure to let the blood droplets fall onto the paper. You don’t want to touch the paper with your finger.

You’ll need to let the paper dry for several hours before packing it up, shipping it off, and then waiting for your results. Most companies give you some indication that your sample has shipped, and LetsGetChecked even provides you with a tracking number so you can follow it to the lab. Most samples yield results within about two days after arriving at the lab. As with in-person testing, you’ll receive an email or text message directing you to your online account, where you can view and download your results.

How the thyroid gland, hormones, and antibodies work

To understand how blood tests help identify thyroid disorders, it’s important to know a bit about the thyroid and the specific substances these thyroid tests measure.

Shaped a bit like a butterfly and located in your neck, the thyroid is an endocrine gland that secretes hormones into the bloodstream. It serves several different functions, most notably regulating your metabolic rate.

When ordering a thyroid test, you will come across a lot of terminology that can be confusing. Here is a breakdown of the typical cast of characters in these tests, along with some explanation.

T4 (thyroxine)

Thyroxine is the primary hormone produced by the thyroid gland. We call it T4 because it contains four iodine atoms. In our bodies, T4 plays vital roles in the health of our heart, digestive system, brain, bones, and metabolism.

T3 (triiodothyronine)

In our bodies, blood carries T4 to various organs — such as the liver, brain, and kidneys, to name a few — where its actions cost it an iodine atom, converting T4 to T3 (triiodothyronine). The thyroid gland produces some of the body’s T3, but only a tiny fraction of the amount resulting from T4 conversion.

TSH (thyroid-stimulating hormone)

As its name suggests, thyroid-stimulating hormone (TSH) signals the thyroid to produce additional T4. When T4 levels in the bloodstream are low, the hypothalamus produces thyrotropin-releasing hormone (TRH), which in turn causes the pituitary gland to secrete TSH. When that TSH hits the thyroid gland, it pumps out T4 in response.

Free T4

A thyroid blood test needs to measure “free T4” (sometimes written as FT4 or FTI/T7). Free T4 is the thyroxine that is not bound to proteins and can act on body tissues. It is more valuable to measure free T4 — rather than only total T4 — along with TSH to detect whether a thyroid disorder is present.

Thyroid antibodies (TPO/TPEX and TgAb)

When attacking a dangerous substance like bacteria, your body’s immune system uses antibodies. But in the case of an autoimmune disorder, our body unleashes those antibodies on some aspect of itself. In this case, there are autoimmune disorders that attack the thyroid gland. Two common antibodies in this scenario are thyroid peroxidase antibody (TPO/TPEX) and thyroglobulin antibody (TgAb).

TRH (thyrotropin-releasing hormone)

What controls the pituitary gland’s release of TSH? That would be the hypothalamus and its production of TRH. When the hypothalamus produces TRH, it causes the pituitary gland to produce TSH.

Knowing the nature of these different substances reveals why thyroid blood tests are a powerful tool in identifying disorders. You could think of the hormonal regulation of a healthy thyroid as being a little like a thermostat. When a room gets too hot or cold, the thermostat signals to the radiator to produce more or less heat. This constant signal and response keeps the room at a stable temperature.

Similarly, based on how much T4 is already present in the bloodstream, hormones from the hypothalamus and pituitary gland signal to the thyroid that it needs to produce more or less T4 to keep the organs and systems of our body stable. But what happens when the thermostat or radiator doesn’t function properly? Abnormal levels of TSH, T3, or T4 indicate that the finely tuned system is out of balance.

How thyroid tests indicate possible disorders

Thyroid tests like those in this guide use blood to measure the concentration of thyroid hormones circulating in the body. These can combine with other tests to get more detailed information about an underlying disorder.

TSH testing

The TSH level is a crucial measurement — often the first hormone doctors measure — when investigating a potential thyroid problem. High levels of TSH may suggest that the thyroid is underactive due to an issue affecting the gland directly. Conversely, low levels of TSH indicate that the thyroid is overactive.

This may be due to a problem affecting the thyroid directly or a problem affecting pituitary gland function. There is quite a bit of important insight that a TSH measurement alone cannot provide. For example, the TSH blood test does not give any information on T4 converting into T3 or if T3 receptors are resistant to the T3 hormone. A TSH blood test alone also can’t tell us if the immune system is attacking the thyroid, or if the body is deficient in minerals and vitamins needed for thyroid health.

Additionally, measuring the T4 and T3 values in a thyroid panel gives doctors much more information that can help them arrive at a diagnosis more quickly. The three values together (TSH, T4, and T3) provide a baseline for understanding whether a thyroid disorder exists.

T4 testing

The thyroid hormone T4 (thyroxine) circulates in the blood in two forms:

  • Bound to proteins and consequently prevented from entering cells
  • “Free” and able to enter cells

Measuring free T4 (FT4) together with TSH is most useful when assessing the function of the thyroid.

Low FT4 alongside high TSH could signal hypothyroidism (an underperforming thyroid gland). This type of test result suggests that the pituitary gland is producing more TSH to signal to your thyroid gland that it ought to make more T4. Yet, despite this, the thyroid is not producing enough T4 to reach normal levels.

Meanwhile, if your TSH level is elevated, but your levels of T4 and T3 are normal, you might have what is known as subclinical hypothyroidism.

If your T4 and T3 levels are above normal, while your TSH level is low, you may have hyperthyroidism (overactive thyroid). In this case, your pituitary gland is not telling the thyroid to produce more T4, and yet the thyroid is producing excessive amounts of it.

T3 testing

Doctors usually combine T3 testing with the above tests to determine the severity of hyperthyroidism. The higher the levels are, the worse the thyroid is overproducing. It is rarely helpful in diagnosing hypothyroidism, as the levels of T3 are often stable in that condition.

Thyroid antibody testing

When TSH, free T4, and T3 results suggest a disorder, the next step is a further diagnostic workup to identify the cause. This additional testing often includes a blood sample to measure common thyroid antibodies such as TPO/TPEX and TgAb, in addition to other exams.

The measurement of thyroid antibodies can determine if the thyroid is under attack from the immune system. Your immune system protects your body against foreign invaders by sending antibodies to destroy them. These antibodies come from white blood cells known as lymphocytes, and they sometimes target the thyroid. In individuals with hypothyroidism or hyperthyroidism, lymphocytes often produce antibodies that stimulate or damage the thyroid.

Two common ailments detectable with the help of antibody testing include the following.

  • Hashimoto’s disease — also called Hashimoto’s thyroiditis — is an autoimmune disease in which your own body’s immune system attacks your thyroid, leading to hypothyroidism. The TPO/TPEX and TgAb antibodies may show up alongside low free T4 and elevated TSH.
  • Graves’ disease is an autoimmune disease that causes hyperthyroidism (in which the thyroid produces too much T4). With Graves’ disease, TPO/TPEX will often show up in the blood, in addition to the other signs of hyperthyroidism presented by TSH, T4, and T3 levels.

Thyroid tests that measure TSH, free T4, T3, also thyroid antibodies provide an excellent window into the functioning of the thyroid gland and the potential underlying causes of abnormal test results.

Challenges associated with testing thyroid function

The perfect thyroid test would analyze the levels of thyroid hormones in all of the body’s cells. Unfortunately, this is not possible. Instead, we have to infer information about hormone levels in the cells by measuring levels in the blood.

The difficulties with thyroid testing are often a result of this indirect measuring not effectively communicating complex interactions and processes at a cellular level. For example, the body cells might not be actively taking in the hormones, as the receptors have become resistant. This would mean the blood levels of the hormone would appear normal but may still cause unpleasant or dangerous symptoms.

If you suspect you might have a problem with your thyroid, a doctor will investigate by recording your symptoms and examining your neck to feel if your thyroid might be enlarged. This can be a good indicator of thyroid disease. Usually, blood tests can analyze the amount of thyroid hormones in circulation.

Read this next

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