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5 essential labs to check your thyroid health

Updated: Oct 31, 2023

Why are you tired all of the time!??

Let's be clear- the thyroid is not the only cause for fatigue. Anemia, infections, heart disease, sleep problems, lung disease and many more things can cause fatigue.

But we are going to focus on one cause that affects 12% of the population .... LOW THYROID FUNCTION.

1 in 5 women have a low functioning thyroid.

Did you know that:


If you're wondering whether your symptoms indicate an early-stage thyroid condition, or you'd like to better understand your diagnosed thyroid condition, read on, and feel free to contact us with any questions. 

Hypothyroidism is when the thyroid is not functioning at an optimal level and the brain has to send out a stronger signal to stimulate the thyroid to continue working.


  1. Constipation 

  2. Persistent Fatigue 

  3. Hair Loss 

  4. Muscle and Joint Aches and Pains  

  5. Variable Periods

  6. Unexplainable Weight Gain

  7. Low Appetite 

  8. Hoarse Voice

  9. Brain Fog and Trouble Concentrating 

  10. Sensitivity to Cold 

TSH- might not be enough on its own!

TSH is typically the only lab run to assess normal thyroid function but it doesn't give us the entire picture. TSH is a brain hormone, it is released by the pituitary gland and signals the thyroid to make more thyroid hormone. If TSH is elevated then it means the brain is having to send out a stronger signal to the thyroid since the gland isn't producing optimal levels of thyroid hormone.

Optimal vs Disease

In functional medicine we don't look just at "normal" reference ranges.

This is because "normal" in the US is unfortunately not optimal. A "normal" TSH measurement is between 0.45-4.5μIU/mL.

That's a tenfold difference from one end of "normal" to another. That's a huge range.

Does that mean you feel the same if your value is 4.4 compared to 0.5? No! You will have very varying symptoms based on what your levels are. Optimally, TSH is between 0.5-2.5 μIU/mL.

And if you have Hashimoto's hypothyroidism (see below) then you want your TSH to be as close to 1.0 μIU/mL as possible.

TSH is not the only marker to check

A comprehensive thyroid panel should include free T3, free T4, anti-TPO antibodies, and anti-thyroglobulin antibodies in addition to TSH.

Free T3 (fT3): This is the active thyroid hormone that actually exerts its effect on the cells. It is responsible for energy production, hormone production, regulating bowel movements, and so much more.

Normal: 1.81−4.06 pg/mL

Optimal: 2.5-4.4 pg/mL

Free T4 (fT4): T4 is the majority of the thyroid hormone that is produced. It must get converted to active thyroid hormone (fT3) in order to have any effect in our body. If free T4 is normal but fT3 is low, then you are not converting properly and might require supplementation with nutrients to help this processes along.

Normal: 0.82-1.77 ng/dL

Optimal: 1-1.5 ng/dL

Thyroid Peroxidase Antibodies (TPO antibodies): 90% of the individuals who have hypothyroidism have autoimmune hypothyroidism (Hashimoto’s disease). TPO is one of the markers for Hashimoto’s. It is important to know the cause of hypothyroidism because you treat it differently from non-autoimmune hypothyroidism.

Normal: 0−34 IU/mL

Optimal: 0 IU/mL

Anti-thyroglobulin antibodies: Another marker for autoimmune thyroid disorder (Hashimoto’s).

Normal: 1-115 IU/mL

Optimal: 0 IU/mL

Next Steps:

If you struggle with thyroid issues or have not yet tested your thyroid and are interested in working with a modrn med doctor, now is the time to do so! Click here to become a patient today.

For a list of Dr. Mary's "optimal" lab ranges click here.

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