Hypothyroidism, or low thyroid function, is a problem that impacts millions of Americans—especially women! An unhappy thyroid can cause symptoms like fatigue, hair loss, weight gain, dry skin, constipation, irregular periods, miscarriages, chronic pain, brain fog, reflux, anxiety, and depression.

Unfortunately, the lab testing many doctors order doesn’t adequately screen for thyroid problems. Which is exactly why you or someone you love may be hearing that your labs are normal, even though you know something is wrong!

Typical Thyroid Testing Falls Short

The standard of care in conventional medicine for evaluating thyroid function is to run a TSH (thyroid stimulating hormone). Some doctors will also order a total T4 (or sometimes a free T4), but most don’t. 

Here’s the problem with that: TSH (with or without T4) does NOT give us the full picture when it comes to your thyroid health—meaning your doctor may be missing a very real problem with your thyroid! So read on to learn about the 9 thyroid tests I recommend getting EVERY year. 

9 Thyroid Labs to Get EVERY Year!

TSH (Thyroid Stimulating Hormone)

TSH is a hormone that gets secreted by your brain (specifically from your anterior pituitary gland). It tells your thyroid gland to make thyroid hormone. When TSH is elevated, your brain is yelling at your thyroid to make more hormones because there aren’t enough circulating around the body. This is why doctors measure TSH, and that’s a good thing! An elevated TSH alone is enough to diagnose hypothyroidism.

But if your TSH is normal, that doesn’t mean your thyroid is doing its job or that you don’t have symptoms of low thyroid function. Because what TSH doesn’t tell us is how your thyroid is responding to that signal from your brain!  And if your TSH is on the lower end, that could mean your brain is asleep on the job (stress, inflammation, and stealth infections are three common culprits)—especially if your thyroid hormones are also low, which you can’t know unless you test them!

Thyroid Hormones: Total T4, Total T3, Free T4, Free T3

Your thyroid gland makes thyroid hormones—mostly thyroxine, or T4 (the inactive form), but also some triiodothyronine, or T3 (the active form). The active form (T3) is what interacts with your cells at the level of your DNA (yes, thyroid hormone is THAT important).

When your body needs more active thyroid hormone (T3), it will actually convert T4 into T3. This process of converting T4 into T3 requires several nutrients and happens primarily in your liver and gut. This is a major reason why your thyroid function is impacted by the rest of your health and why it’s SO important to take a whole-body approach when it comes to assessing—and addressing—your thyroid! 

In order to know how your thyroid gland is responding to the TSH your brain is secreting, you’ve got to know what your T4 and T3 levels are. Total T4 and total T3 measure just that—the total amount of T4 and T3 in your bloodstream, and this is really important info!

But knowing your total T4 and total T3 doesn’t tell you how much of your thyroid hormones are free, meaning they aren’t bound to proteins and are available to do their jobs (in the case of T4, that’s getting converted into T3; in the case of T3, that’s impacting nearly every cell in your body!). This is why measuring free T4 and free T3 is crucial when it comes to assessing thyroid health.

Reverse T3 (rT3)

In addition to converting T4 into T3, your body also converts a small percentage of T4 into reverse T3 (rT3), which is inactive and NOT the same as T3. And once rT3 has been made, that conversion can’t be undone. This is actually a failsafe mechanism to ensure you don’t end up making too much T3. The body is brilliant!

When you are super stressed (this can be physical or psychological stress) or dealing with lots of inflammation or a significant chronic illness, your body can start converting T4 into rT3 at a much higher rate, which will then affect how much T4 turns into T3. When this happens, you can have normal levels of TSH and total and free T4…but because your body is converting too much of your T4 into rT3 instead of T3, you can still suffer from symptoms of hypothyroidism!

T3 Uptake

T4 and T3 travel around the body attached to proteins, so the amount of these proteins can impact how much thyroid hormone is available for use. Remember, it’s the free—or unbound—T4 and T3 that actually get used by the body. T3 uptake is an indirect measurement of the amount of these thyroid hormone binding proteins, which are kind of like school busses for thyroid hormone.

When there are lots of busses available, more thyroid hormone will be on the busses and less will be available for use, or “free”.  In this case, the T3 uptake will come back low, and you may experience symptoms of hypothyroidism as a result of too many busses (excess binding proteins). 

On the flip side, when there aren’t many busses available, more thyroid hormone will be hanging around “free” (single and ready to mingle!), so T3 uptake will be high. While in some individuals this may create symptoms of hyperthyroidism, it’s more likely that over time you will develop what’s known as thyroid receptor-site resistance. Basically your thyroid receptors get used to so much thyroid hormone hanging around and they become less sensitive to it. This can lead to symptoms of thyroid hypofunction.

Testosterone and estrogen can both impact thyroid-binding protein levels and, therefore, T3 uptake. This means that sex hormone imbalances and mismanaged hormone replacement therapy (HRT) can directly affect your thyroid hormone levels! With that said, it’s important for you to know that significant sex hormone imbalances can exist without seeing shifts in T3 uptake levels, so if you have a normal T3 uptake, that does NOT rule out the presence of sex hormone imbalances.

Thyroid Antibodies: Anti-Thyroperoxidase (Anti-TPO), Anti-Thyroglobulin

It’s estimated that up to 90% of hypothyroidism is autoimmune in nature, and these thyroid antibodies can be elevated YEARS before clinical disease is present, which is why I suggest every woman get these antibodies tested annually!

If autoimmunity to your thyroid gland is developing, you want to know BEFORE it starts creating problems for you so that you can work with someone to identify the root causes of your immune dysfunction and do what you can to prevent the destruction of your thyroid gland and the development of Hashimoto’s hypothyroidism. 

And if you have hypothyroidism already, or suspect that you do, you want to know if there is autoimmunity happening because that requires taking a different approach to really address the issue. In the case of thyroid autoimmunity, the real problem isn’t your thyroid gland—it’s your immune system! (And actually, it goes deeper than that because then the question is what’s triggering your immune system dysfunction?).

In the case of thyroid autoimmunity, thyroid hormone replacement can correct thyroid hormone levels (and this is important!), but it’s crucial for you to know that thyroid medication does NOTHING to address the immune system dysfunction that is actually causing your thyroid dysfunction! And if that aspect is not addressed, the immune system dysfunction continues, the damage to your thyroid gland continues, and over time you will need higher and higher doses of medication to keep your thyroid hormone levels in the normal range. Plus, other areas of your health will suffer because of that immune dysfunction and the chronic inflammation that comes with it…NOT good!

On A Budget? 6 Essential Labs to ID a Thyroid Problem

If you need to pare down that list, these are the six thyroid labs that I consider essential to evaluating the health of your thyroid:

1. TSH
2. free T3
3. free T4
4. reverse T3 (rT3)
5. anti-TPO
6. anti-thyroglobulin

Remember, these labs are only a snapshot in time, so they don’t tell the whole story! And because each of these markers provides a different piece of the puzzle, they have to be interpreted together and within the context of your whole symptom picture if you want to really understand what’s happening with your thyroid gland. Ideally they should also be from the same blood draw, with additional parameters met for fasting status, time of day, supplement avoidance, and timing of your thyroid meds if taking any.

However, even if all these results come back “normal,” that doesn’t mean there isn’t some thyroid dysfunction happening! The reference ranges that labs use are meant to identify disease, not health. Using functional lab ranges can provide valuable insight when it comes to understanding what’s going on in your body and why you’re experiencing symptoms.

Keep in mind that blood sugar + insulin regulation, inflammation, nutritional status, adrenal function, sex hormone balance, and the health of your gut and liver can all impact how much thyroid hormone you’re making and your ability to use your thyroid hormones—which is why you can have normal lab results and still be dealing with hypothyroid symptoms! This is why it’s so important to work with a knowledgeable healthcare practitioner, particularly someone trained in naturopathic or functional medicine, who can help you correctly interpret these results in light of your medical history and complete health picture.

Take Charge of Your Health!

I hope you found this helpful! Thyroid health is a BIG topic, and there are actually SIX different types of hypothyroidism (read more about that here)!! This is why it’s SO important to get comprehensive thyroid testing!

If you want more support on your healing journey, I’d love to work with you! Learn more about my services here.