UNDERSTANDING THYROID TESTS

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Scary, isn’t it?!

When you realize that your body isn’t performing like it normally should. Something is off and you aren’t sure how you ended up here. How did you miss the signs so easily?

This is how I felt after my very first doctor appointment when I learned that my thyroid was beginning to fail (find more about that in Part 1: What is Hashimoto’s Thyroiditis?). This wasn’t supposed to happen to me! After this harsh wake up call, I realized that it was time to figure out exactly what is going on with my thyroid. Here is what I learned.

Your thyroid creates several hormones- T1, T2, T3, and T4. Two of the more important hormones secreted by your thyroid are T3 (triiodothyronine) and T4 (thyroxine). T3 is the active hormone that is used by our bodies for energy and is three times more potent than T4. T4 is an inactive, storage hormone that is converted by our bodies to T3 as needed.

Although your thyroid makes both of these hormones, it makes only a small amount of T3 and a much larger amount of T4. When diagnosed with Hashimoto’s Thyroiditis, your thyroid is no longer able to make the correct amounts of these hormones due to being attacked by your immune system. You may find yourself with an under-active thyroid and many awful symptoms are likely to follow. My worst symptoms were extreme fatigue and a low body temperature although there were many others you can read about in 15 Key Symptoms of Hypothyroidism.

GETTING FAMILIAR WITH THE THYROID TESTS

While I was waiting for the results of my second blood test to verify my thyroid failure, I tried to get an idea of what I was dealing with. There are many tests that can show how your thyroid is functioning. Understanding the results of these tests can be confusing so I wanted to include a short explanation for each one.

The main tests used for your thyroid function are a Thyroid Stimulating Hormone (TSH), Free T3, Total T3, Reverse T3, Free T4, Total T4, Thyroid Peroxidase Antibody (TPO), and Thyroglobulin Antibody (TgAB). I have created the table below to try to organize the definitions of these test.

My doctor did not run all the tests listed above, however, she ran enough of them the second time around to show that my thyroid was struggling. Originally, my first test for TSH came back at 4.38 uIU/mL in the “healthy” range. However, when my doctor ran my TSH test again it came back higher at a 6.52 uIU/mL.

I remember being so relieved. It was the proof I needed to convince her that I was not feeling normal. She finally agreed that I had hypothyroidism and referred me to an Endocrinologist.

I didn’t know much about these tests and it took some time before I really was able to fit everything together. I remember being completely confused and overwhelmed. Let me do my best to explain my results now that I have a better understanding of my condition. I am not a doctor and I am not giving medical advice. By giving these ranges, I am hoping to help you get a better idea of what these tests mean- something that took me a long journey.

EXPLANATION OF MY RESULTS

The TSH test is the “gold standard” according to doctors for judging thyroid issues relating to hypothyroidism. TSH is actually a hormone released by your pituitary gland that tells your thyroid to produce more or less thyroid hormones. When your TSH test is high, it is because your pituitary gland is telling your thyroid gland to produce more thyroid hormones. If your thyroid is unable to fulfill this request then you may experience symptoms of hypothyroidism like I did.

Generally, a healthy person would have a TSH reading between a 1 and 2.5 uIU/mL, but many doctors won’t treat you unless it is over a 4 or 5 uIU/ml – sometimes up to a 10 uIU/mL – even if you are experiencing severe symptoms. You can find more on the common symptoms of hypothyroidism by reading 15 Key Symptoms of Hypothyroidism.

Here are the results from my second round of tests:

Lab Test	My Results	Lab Range
TSH	6.52 uIU/mL	0.34 – 4.82 uIU/mL
Free T3	2.77 pg/mL	2.3 – 4.2 pg/mL
Free T4	0.72 ng/dL	0.59 -1.61 ng/dL
TPO	200 IU/mL	Standard range <35 IU/mL

The TSH test alone can be short sighted because it doesn’t tell the whole story. Many people will continue to have a healthy TSH while also having high TPO and TgAB antibodies – showing that their thyroid is under attack. To get a clear picture you really need to run more than a TSH test. As you can see above, my second TSH result of 6.52 uIU/mL is in the unhealthy range.

The next test, Free T3, is a good indicator of your energy levels. Free means unbound and available to be used in your blood. A healthy Free T3 reading would be somewhere between a 3 or 4.2 pg/mL- however, optimal is at the top half of the range.

The following test is for Free T4. T4 is inactive and is what is converted to T3. A healthy range for Free T4 is somewhere between a 1 and 1.4 ng/dL.

The last test, TPO, is testing a specific type of thyroid autoantibodies that shows that your body is creating antibodies against your thyroid. You can see that my TPO antibodies are elevated showing autoimmune disease- Hashimoto’s Thyroiditis. I have read that when these TPO antibodies get above 120 IU/mL your symptoms become more severe. Some people disagree with this although this proved to be true for me.

Usually, you are looking for these antibodies to be less than 9 IU/mL in a healthy individual, but every lab seems to judge this differently. As you can see the lab above looks for less than 35 IU/mL.

Like I said, I am not an expert, however, I wanted to give you optimal values based on my research because it was really hard for me to find and understand these tests in the beginning of my experience. Here is a website that reviews these tests in more detail if you would like more information.

From the tests above, you can see that my Free T3 and Free T4 were in the lower ranges and that my TSH and TPO are out of range so my next step was to the Endocrinologist. At the time, I thought this was going to solve my problems, but I later learned that it was just the beginning of them.

I also want to mention that this webpage from Stop the Thyroid Madness is a wonderful reference for understanding lab values if you need a more in depth answer.

Click here to go to Part 1: What is Hashimoto’s Thyroiditis? of this series. In Part 3: The Great Thyroid Medication Debate on my thyroid journey, I will tell you how that first visit to the Endocrinologist went!