Every cell in our body contains receptor sites for thyroid hormones. Thyroid hormones are responsible for the most basic and fundamental aspect of our physiology, metabolism and more. Our thyroid is the center of our cellular metabolism and is extremely sensitive to minor imbalances in our bodies. Thyroid dysfunction is prevalent in our society and can lead to a loss of function, neurological symptoms, and a reduction in quality of life.
The importance of thyroid function on our health:
Our thyroid health is extremely sensitive to other imbalances in our bodies: other types of endocrine imbalances, environmental factors/toxins, cross reactions to medications, and more.
In this blog post, we are will journey through the steps in thyroid metabolism and explore why it is so important to evaluate all thyroid markers when evaluating our overall health – especially brain health.
Thyroid metabolism begins in our brain! To begin the process of creating thyroid hormone our hypothalamus, which is a group of cell bodies located at the base of your brain, produce thyrotropin releasing hormone (TRH). This area of our brain (our hypothalamus) is heavily influenced by dopamine and serotonin neurotransmitters. Meaning any factor that disrupts the creation of these transmitters will affect your thyroid. Some things that negatively affect the dopamine and serotonin pathways in the brain are diet, gut health, stress, sleep, screen time, and medications.
After TRH has been released, our pituitary gland is stimulated. The pituitary gland then releases thyroid-stimulating hormone (TSH). TSH circulating in our blood stream causes our cells to create thyroid peroxidase (TPO). TPO then produces T4 and T3 by transporting iodine to our thyroid. Our thyroid gland then produces T4 and T3. The majority of the hormone production in the thyroid is inactive T4. Our bodies cannot utilize T4, so it has to convert T4 into T3 to become useful to our system.
How does T4 become active so our body can use it?
Once our thyroid has produced T4, it releases it into our bloodstream where it is circulated and metabolized by our liver. At our liver, T4 is then converted into a few things. It is mostly converted into T3, but some of it is converted into reverse T3 and the rest is converted into T3 sulfate and T3AC. These final two T3 hormones (T3 sulfate and T3AC) are inactive circulating in our blood stream as well. To become active they must reach our digestive system. Once they reach our digestive system, an enzyme called intestinal sulfatase reacts with them and turns them into active T3. Intestinal sulfatase activity is dependent upon healthy gut microflora. Then the active T3 circulates back into our bloodstream and binds to thyroid receptors on target tissue and promotes mitochondrial activity and the activation of cellular metabolic rate.
All of this means that our thyroid health and our bodies ability to receive thyroid hormones is dependent on our brain function, liver function, gut health and circulation. In return our thyroid influences our brain function, hormone regulation, neurotransmitter production, immune function, digestive function and more. A proper thyroid evaluation is a very important part of our evaluation at CFNC.
Why do we run a full thyroid panel?
Incorporated into our new patient blood work is a full thyroid panel with antibodies. This panel allows us to understand where in the multiple steps of thyroid metabolism we are having dysfunction. This panel allows us to go beyond just TSH, T3 and T4 and understand why our patient may be having thyroid dysfunction. Is it as a result of their gut health? Is it a brain-based thyroid dysfunction? Is it an immune or autoimmune issue?
The different thyroid markers such as Reverse T3, T3 uptake, Free T4 and T4 tell us which system in the body is having difficulty, other than just the thyroid.
Thyroid dysfunction can manifest as neurological symptoms and/or perpetuate neurological symptoms. It is crucial to evaluate all of the thyroid markers when understanding the origination of our patients symptoms.
Which thyroid markers are in our thyroid panel and what does each marker indicate?
Thyroid Stimulating Hormone (TSH)
This hormone is also called thyrotropin. This hormone is released by the pituitary gland and is the most common marker used to assess thyroid function and is also the most sensitive. TSH levels increase when the T4 levels drop and TSH falls when T4 levels increase. This is the only test performed in traditional healthcare as it screens the patient for thyroid disorders and the need for thyroid hormone replacement therapy. On the other hand, evaluating this level alone does not provide information about optimal physiological function of the individual’s thyroid. TSH alone does not consider peripheral thyroid metabolism, thyroid-brain feedback loops or evaluate antibodies.
Thyroxine (T4)
T4 is produced directly from our thyroid. This test measures both bound and unbound thyroxine levels. Therefore it does not provide a lot of information if it is measured alone. The majority of our thyroid hormone produced by our thyroid is T4, and T4 is not useful to our bodies. Our system then has to convert the T4 to T3 for our bodies to utilize the hormone.
Free Thyroxine Index (FTI)
FTI is measured by multiplying the total levels of T4 by the T3 uptake levels. The result is Free T4, which is the amount of active T4 available in our blood stream. Thyroid hormones are transported through our blood stream by being bound to protein in our blood. Not all thyroid hormones are bound to protein in the blood. FTI helps us calculate the total Free T4 and that will provide us with insight on how much T4 is available to the body to be converted.
Free Thyroxine (Free T4)
This test is used to measure the amount of free and active T4 available to the body. This level in conjunction with TSH can provide the diagnosis of hypothyroidism.
Total Triiodothyronine (T3)
Total T3 is the total t3 concentration in the blood and is the test to confirm thyrotoxicosis. This test is used to diagnose hypothyroidism and help identify peripheral down regulations in the conversion of T4 to T3.
Resin T3 Uptake
Resin T3 uptake measures the amount of sites for active unbound T3 circulating in our blood stream. The more binding sites that are open on the proteins, the lower the resin uptake result will be. For example, birth control that has estrogen in it will raise the amount of binding sites. This will cause T3 uptake to be reduced. Testosterone on the other hand decreases the amount of binding sites and will cause an increase in T3 uptake.
Free T3
This blood level measures the amount of free T3 hormone. This test is the best marker to see what amount of active T3 is available to our body’s thyroid receptor sites.
Reverse T3
When T4 is converted into T3, sometimes it can be converted into reverse T3. Revere T3 and T3 can both bind to our thyroid receptors on our cells, although when reverse T binds to them, nothing happens. Reverse T3 is typically produced during major traumas, elevated stress responses or chronic stress.
Thyroid-Binding Globulin
TBG binds thyroid hormones in circulation. It is the main protein that is responsible for carrying both T4 and T3 in the blood stream. This level can help to determine patterns of thyroid imbalances.
Thyroid Antibodies (TPO Ab, Tg Ab and TSH-R Ab)
Thyroid antibodies indicate that the body’s immune system is forming a response and attacking its thyroid tissue. Production of antibodies may create a hypothyroid or a hyperthyroid state. This is important to evaluate if thyroid dysfunction is thyroid mediated or immune mediated.
Our Approach
Proper thyroid assessment and evaluation is a crucial part to our examination and approach at CNFC. Evaluating thyroid function helps to uncover the origin of someone’s symptoms as well as help them achieve optimal brain health. A part of our new patient exam at CFNC, every patient receives lab work that includes a full thyroid panel with antibodies.