Most Important Thyroid Tests and How to Interpret Them

Frequently in my practice I meet ladies who don’t know they have autoimmune Hashimoto’s because still, to this day, most conventional care doctors do not perform comprehensive thyroid testing to confirm it. Even more frequently, I meet ladies whose thyroid medications are not as effective as they could be because of the lack of comprehensive thyroid testing.

As you can imagine, many cases of autoimmune thyroid problems are missed because of inadequate investigation by physicians. And rarely are those with Hashimoto’s, with or without hypothyroidism, actually informed by their physicians that they have an autoimmune condition progressively destroying their thyroid gland.

I believe I spent nearly two decades undiagnosed because the correct bio markers were never evaluated by my trusted physicians. Hashimoto’s was missed completely and hypothyroidism was only diagnosed once it reached a later stage of decline. By that point I was already suffering significantly with deep fatigue, unexplained weight gain, sleep issues, depression, chronic body pain, and most discouraging of all for me, brain dysfunction.

I am on a MISSION to educate as many ladies as I possibly can on when it is appropriate to do more comprehensive testing to uncover early Hashimoto’s BEFORE thyroid decline and for those with established hypothyroidism, determining if it is autoimmune in origin, then how to slow progression and get their lives back so they can THRIVE!

No one should have to suffer when there are answers and many easy ways they can implement to slow decline.

If you have or suspect that you may have a thyroid condition, or know someone who does, this extensive blog article will review all of the most helpful tests that can help you identify a thyroid condition and hopefully help you understand what the labs mean so you can be a better advocate for yourself when requesting conventional care.

This article will also teach you how to understand your labs so that you can advocate for proper treatment for yourself.

The ABC’s of Thyroid Tests

The first step in diagnosing a thyroid condition and figuring out a treatment plan is testing thyroid bio markers via a blood test. However, if your thyroid hormones are determined to be within normal range yet you still suffer with many symptoms of hypothyroidism, you would need to request testing of specific immune antibodies for a Hashimoto’s diagnosis. Unfortunately, many doctors will refuse to test those markers when thyroid hormone levels are normal even though research has shown that antibodies against the thyroid can be elevated 7-10 years before onset of hypothyroidism!

Typically, conventional physicians are trained to test TSH (thyroid stimulating hormone) and sometimes free T4. It they are within the normal range, they usually will not test further. These two tests do not help determine if Hashimoto’s is at play, nor can they always catch the beginnings of hypothyroidism.

For all these reasons, I recommend you have a full thyroid panel done which include TSH, free T4, free T3, TPO (thyroperoxidase) and Tg (thyroglobulin) antibodies. I also recommend having a baseline thyroid ultrasound performed to determine if there is any physical changes to the thyroid. Altogether, this information can diagnose both Hashimoto’s and hypothyroidism.

Ordering Lab Tests

If your physician or nurse practitioner is ordering the thyroid labs for you, be sure to request a copy so that you can see them for yourself and ensure that they are interpreted correctly. I encourage everyone to keep their test results in a file or binder so it’s easy to track progress or decline over time.

If your physician or nurse practitioner refuse to evaluate your thyroid bio markers, I suggest finding a new professional who will see you as an important part of your health team.

In Canada, it is unfortunately very difficult to get access to self-order options for lab testing. If you live in Lethbridge where I practice, I can send you to the local hospital with a cash pay lab kit specifically for the array of thyroid bio markers. If you live elsewhere, consider asking a Naturopath for assistance as they can usually send you for cash pay blood work depending on your location. Even some pharmacists can request bloodwork now in some areas. Ask around. Don’t stop trying to find someone to help you get the testing done. Your health may depend on it.

Thyroid Hormones to Test

TSH (Thyroid Stimulating Hormone)

TSH is used conventionally as a screening test for thyroid disease, as well as a test for monitoring the correct dose of replacement thyroid hormone medication needed for an individual.

TSH is a hormone produced in the pituitary gland in the brain that is carefully controlled in response to T4 (thyroxine) hormone circulating in the blood. If TSH is elevated, it means that you do not have enough thyroid hormone available to your cells at that time. The rise in TSH is meant to stimulate the thyroid gland to produce more T4. If the thyroid gland cannot produce enough T4, you are likely hypothyroid.

At advanced stages of Hashimoto’s and with primary hypothyroidism, TSH will be elevated. In the case of Graves’ disease and hyperthyroidism, TSH levels will be low. People with early stages of Hashimoto’s and central hypothyroidism. TSH may still be within normal range.

The National Academy of Clinical Biochemists has indicated that 95% of individuals without thyroid disease have TSH concentrations below 2.5 μIU/mL, and a new normal reference range was defined by the American College of Clinical Endocrinologists to be between 0.3-3.0 μIU/mL. However, most laboratories have not yet adjusted that range in the reports they provide to physicians. Some outdated ranges are as extreme as 0.2-8.0 μIU/mL! If that range is followed, it would lead to a patient being told that their thyroid is normal, when in fact, they have a thyroid condition.

Functional medicine practitioners have gone a step further and defined the normal reference range to be between 1-2 μIU/mL for a healthy person not taking thyroid medications. Even when taking thyroid medications though, most patients in my experience, including myself, feel best when our TSH is between 1 and 2 uIU/mL. It is important to figure out your sweet spot and the only way to ensure you are there is to always request a copy of your bloodwork so you can verify and track.

As a thyroid condition progresses, a lot of fluctuation of thyroid hormones can occur. Therefore, TSH is not the only test that should be used to monitor your condition or to diagnose Hashimoto’s.

Disappointingly, most conventional physicians will not test other markers if TSH is within normal range, even if you are experiencing major hypothyroid symptoms. This is why you need to also investigate other markers and track them over time too.

Recommended test: TSH

Optimal reference range: between 0.5-2 μIU/mL

How often you should test: Every 4-6 weeks when starting a new medication, then every 6 months if symptoms are stable.

T1, T2, T3 and T4

There are four main thyroid hormones that have been identified by science so far: T1, T2, T3 and T4.

The main hormones we can test in labs are T4 (thyroxine) and T3 (triiodothyronine). T4 is known as pro-hormone and is 300 percent less biologically active than T3. That doesn’t mean it doesn’t do anything, but T3 is the main biologically active thyroid hormone that influences nearly every cell in your body! Once T3 enters cells, it can trigger biochemistry that impacts the quality of your hair, your energy level, your metabolism and more.

The most commonly prescribed thyroid medications are Synthroid and levothyroixine. These are T4 only. Because your body requires T3 for functions, your body has to convert the T4 in those medications to the active T3 hormone. Not everyone converts T4 to T3 efficiently, so as you can imagine, those people would have more symptoms than someone who can convert well.

Additionally, when you are under extreme stress, especially chronically, your body in its wisdom will slow you down by making it less likely that T3 can enter cells. This will also mean you’ll have more symptoms of hypothyroidism.

Factors that can impact T4 to T3 conversion:

  • Chronic stress or trauma
  • Aging
  • Alcohol
  • Fasting
  • Kidney and Liver disease
  • Low progesterone
  • Low growth hormone
  • Radiation
  • Chemotherapy
  • Pesticides exposure
  • Cigarettes
  • Heavy metal exposure
  • Certain medications
  • Soy
  • Nutrient deficiencies
  • Obesity
  • Diabetes
  • Surgery

Luckily, we can test T4 and T3 in labs and their levels and ratios can give us insight into how the body is managing thyroid hormones.

You can have normal TSH and normal T4 with low T3. This illustrates issues with conversion that could be investigated.

You also can have normal TSH with low T4 and low T3. This may indicate a rare type of hypothyroidism called central hypothyroidism and it requires more investigation.

Recommended test:Free T3 and Free T4 (FT4, FT3)

Optimal T4 reference range: 15-23 pmol/L

Optimal T3 reference range: 5-7 pmol/L

How often you should test: Every 4-6 weeks when starting a new medication, every 2-3 months if tracking lifestyle change impact, and then every 6-12 months once symptoms are stable.

Thyroid Antibodies

To verify if autoimmunity is at play against your thyroid, at least two immune antibodies need to be evaluated. The presence of higher levels of thyroid antibodies indicate that the thyroid gland has become recognized as a foreign object by the immune system and the immune system will mount attacks against the thyroid gland.

In Hashimoto’s, a myriad of triggers can contribute to the body developing “a lack of self-tolerance.” This is when the body is no longer able to recognize its own tissue as part of itself, but instead starts viewing its tissue as a foreign object. A major purpose of the immune system is to protect you from foreign objects, so you can imagine what can happen when a self tissue becomes viewed as foreign. Elevated antibodies are an indication of this decline in self-tolerance.

In is estimated that about 80 – 95% of patients with Hashimoto’s have thyroid antibodies. They can be elevated at least 7-10 years (or more) before a change in TSH is even detected. Continued elevated thyroid antibodies, even when your TSH is normal, means that it’s only a matter of time before your thyroid becomes destroyed to the point it can no longer produce a sufficient amount of hormones and you become hypothyroid.

I’ve heard some health professionals say that once you have thyroid antibodies, you will always have thyroid antibodies, so the actual number doesn’t matter since the antibodies can randomly fluctuate. I agree with some other professionals that antibodies will fluctuate in response to triggers, such as trauma, infections, etc, and be very helpful as markers of disease progression or remission.

The most common antibodies in Hashimoto’s that are also easy to test in labs are thyroid peroxidase antibodies (TPO antibodies) and thyroglobulin antibodies (Tg antibodies). Most people with Hashimoto’s will have an elevation of one or both of these antibodies. TPO antibodies are definitely the most common ones to see elevated.

However, I have seen low TPO antibodies with elevated Tg antibodies in many Hashimoto’s patients. Therefore, please have both tested to verify autoimmunity.

People with Graves’ disease and thyroid cancer may also have an elevation in TPO and/or Tg antibodies. However, the most common antibodies found in Graves’ disease are TSH receptor antibodies, including thyroid-stimulating immunoglobulin (TSI). This marker is elevated in over 90 percent of people with Graves’ disease. TSH receptor binding antibody (TRAb) – aka TSH-binding inhibiting immunoglobulin or TBII, is yet another antibody elevated in over 50 percent of people with Graves’ disease.

Thyroid antibodies can be used to diagnose a thyroid condition and can be monitored to track progression or remission. Remember, elevated thyroid antibodies indicate that active destruction is happening at your thyroid. This destruction often comes with a lot of symptoms that may cause, or be misdiagnosed, as depression, panic attacks, anxiety, miscarriage, infertility, carpal tunnel, hair loss, weight gain, fatigue, and sadly, hypochondria.

Now for some happy news!

When you have elevated antibodies with a normal TSH, you have the potential to reverse all your symptoms and prevent worsening damage to your thyroid gland all by consistently applying some lifestyle changes and removing as many immune triggers as possible. That’s exciting news that I wish was being shared with everyone so they can get ahead of decline earlier in life.

Unfortunately, most people won’t find out autoimmunity is at play until their thyroid is mostly destroyed and they are dependent on thyroid medications.

Please learn from my story and understand how to evaluate your bloodwork! When I was 42 years old, I missed out on opportunities to interrupt my thyroid’s decline because I didn’t request copies of my bloodwork from physicians to verify their “everything is normal” responses. I’ve seen those lab results and would have recognized a problem then. But instead of trusting myself, I only trusted the physicians with my health. My symptoms continued to decline dramatically until I finally insisted another physician investigate antibody levels at which point it was absolutely clear I was in a later stage of autoimmune thyroid decline. The physicians I met with at that time did not believe there were any other interventions I could make beyond thyroid medications to slow the autoimmune decline. Gratefully I already knew much of what I could do and started doing them the same day I was diagnosed and I recovered a great deal of function as the result! At first, I was angry no one caught the decline earlier. But I’ve since accepted responsibility for not paying enough attention and now ensure I always review my test work, so I miss less and have more control. You also have a lot of say in the trajectory of your own health journey. I urge you to exercise your rights and be your most powerful advocate and health detective.

As one of my wonderful mentors, Dr. Sachin Patel, says: “The doctor of the future is the patient.”

According to Dr. Izabella Wentz, the Mother of Hashimoto’s, as I like to call her:

Recommended tests: TPO, Tg antibodies for Hashimoto’s (and TSI, TBII for Graves’)

Optimal TPO antibody reference range: <2 IU/mL

Optimal Tg antibody reference range: <2 IU/mL

Optimal TSI antibody reference range: < 0.55 IU/L

Optimal TBII reference range: 16-100 percent inhibition of TSH binding

How often you should test: I recommend monitoring thyroid antibodies every 60-90 days to see if the changes you’re making in your lifestyle are helping you. A reduction in these antibodies, especially when accompanied by a reduction in symptoms, is a good indication that your condition is improving and that you are on the right path with your healing interventions.

Thyroid Ultrasound

Some individuals may have thyroid disease but may not yet have detectable hormone changes evident in their blood work.  Research suggests that 10 – 50% of people with Hashimoto’s may not even test positive for antibodies. In these cases, a person might have a less aggressive version of Hashimoto’s known as antibody negative or seronegative Hashimoto’s or their immune system is weak and cannot produce enough antibodies. In each of these cases a thyroid ultrasound can be used to find physical changes in the thyroid gland that can point to a Hashimoto’s diagnosis.

Changes consistent with Hashimoto’s that can be seen on an ultrasound include, a shrunken or enlarged thyroid, tissue density and texture changes, or abnormal growths (aka nodules). Some growths may indicate an autoimmune process at play while others may indicate benign or cancerous growths, the latter needing further investigation.

Research indicates that 10% of people diagnosed with Hashimoto’s are diagnosed using an ultrasound, so please request one if you suspect you may have a thyroid condition or are struggling with infertility or miscarriages.

If thyroid nodules are found, I recommend having an annual ultrasound to track changes. Many of the lifestyle interventions used to manage Hashimoto’s will lead to the shrinkage of nodules.

Recommended tests: Thyroid Ultrasound needs a physician’s order.

How often you should test: I recommend at least one ultrasound for every person, especially women of childbearing age. 

Reverse T3

The Reverse T3 (rT3) test measures how much of the free active T3 is actually able to bind at thyroid receptors. Reverse T3 is produced in response to stressful situations and binds to thyroid receptors but turns them off instead of activating them. This should tell you that stress, especially chronic stress, is a common cause of low T4 to T3 conversion and will lead to hypothyroid symptoms even if TSH and T4 are normal.

When rT3 is elevated but all other markers appear normal, it can help rule out thyroid and autoimmune conditions in favor of possible adrenal stress. Adrenals should then be further investigated with appropriate testing to uncover any health concerns.

I rarely request rT3 testing but it can perhaps be a useful way to track responses to stressors.

Recommended tests: Reverse T3 (rT3)

Optimal rT3 reference range: 11 – 18 ng/dl

How often you should test: Every six months, if recommended by your integrative physician.

Using Your Symptoms to Track Thyroid Conditions

Are you paying attention to how you feel each day and notice when things are off? Listening to your body and being more aware of changes can be a great opportunity for better management of a thyroid condition. Bloodwork is essential for diagnoses and monitoring if medication dosing is appropriate. But monitoring your own symptoms can interrupt decline early on if you’re paying attention. As symptoms change, they can be indicative of changing thyroid hormone levels and autoimmune flares.

Keep your eyes peeled for these symptoms and investigate further if they are worsening:

  • Slowing metabolism leading to weight gain
  • Forgetfulness
  • Feeling cold or cold intolerance
  • Depression
  • Fatigue
  • Dry skin
  • Constipation
  • Loss of motivation
  • Dry, coarse hair
  • Muscle and joint pain and/or stiffness
  • Muscle cramping
  • A loss of the outer third eyebrow
  • Heavy menstrual periods
  • Infertility
  • Miscarriage
  • Swollen face
  • Slowed heartbeat
  • Brittle nails
  • Vitiligo
  • Food sensitivities

Be mindful of hyperthyroid symptoms as well. This can indicate an overdose of a thyroid medication or a major flare and damage to the thyroid that dumps a lot of thyroid hormone into your system temporarily creating a hyperthyroid response:

  • Palpitations
  • Weight loss
  • Anxiety/Nervousness
  • Bulging eyes
  • Tremors
  • Irritability
  • Infrequent menstrual periods
  • Fatigue
  • Heat intolerance
  • Increased appetite
  • Hair loss
  • Enlarged thyroid gland/goiter
  • Increased sweating
  • Frequent bowel movements
  • Infertility
  • Miscarriage
  • Soft nails
  • Warm, moist palms
  • Insomnia
  • Muscle weakness
  • Food sensitivities

Some of these symptoms may be directly related to insufficient or over-sufficient thyroid hormones, while other symptoms may be due to related issues like digestive problems or infections which are seen in many people with Hashimoto’s.

Determining the triggers of the autoimmunity and learning how to remove or reduce them is always the best way to manage Hashimoto’s.

Recommended tests: Create a heath timeline and use a notebook or chart to keep track of your symptoms.

Reference Range: Score the severity of your symptoms from 1-10, and aim to steadily lower your score by uncovering and addressing your root causes.

How often you should test: I recommend assessing your symptoms on a weekly basis until you feel you have eliminated them.

The Takeaways

It can be a little bit overwhelming to figure out where to start with testing, but I hope the information in this article has helped you understand which thyroid tests you need to ask for, and how to interpret and act on the results.

In Summary

  • If you suspect that you may have Hashimoto’s and/or hypothyroidism, I recommend that you get the following diagnostic tests: blood work for TSH, free T3, free T4, TPO antibodies and Tg antibodies, and a thyroid ultrasound
  • If you suspect that you may have Graves’ disease and/or hyperthyroidism, or have hyperthyroid symptoms that may be due to an autoimmune flare, I recommend that you get the following diagnostic tests: blood work for TSH, free T3, free T4,  TSI antibodies and TBII antibodies, and a thyroid ultrasound
  • If you are monitoring your response to replacement thyroid hormones or thyroid suppressing medications, I recommend checking your TSH, free T3 and free T4 levels every 4-6 weeks until stabilized
  • If you are monitoring for remission, I recommend testing TPO antibodies and Tg antibodies for Hashimoto’s, or TSH receptor antibodies for Graves’, every 3 months

Remember, nobody knows your body like you do! Be an advocate for yourself and insist on proper evaluation if you suspect you are developing Hashimoto’s and/or hypothyroidism. And if indeed the diagnosis is positive for either, remember there is more you can do beyond medications to manage progression. Come find me and I’ll help you! Connect with me on Facebook, read my other Blog articles, and Apply for a Discovery Call to see if working together is the best option.


Dr. Krista Coombs

Dr. Krista Coombs

My name is Krista Coombs and I am the owner and practicing Doctor of Traditional Chinese Medicine (DTCM) at AcuPlus Wellness Clinic. I have been treating patients since 2001 using Traditional Chinese medicine (TCM) to help them improve their health. Recently I started pursuing certification in Functional medicine (FM) as well to offer even more health services.

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