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  • Writer's pictureErin Stefanacci

Your Thyroid - From a Functional Perspective: Part 1

January is national Thyroid Awareness Month and rightly so. It is estimated that of the 20 million Americans who have some form of thyroid disease, only 40% know of their condition; meaning 60% of Americans who have a thyroid condition aren’t even aware. It’s time we start talking about our thyroid.

The thyroid gland is a small butterfly-shaped gland that sits at the base of your neck. Thyroid hormones are necessary for every cell in the body to function properly. Some might be shocked to find out that the thyroid affects heart rate, body temperature, muscle strength, cholesterol levels, and even more!

Hypothyroidism and Hashimoto’s Disease are the most common thyroid disorders. Both of these conditions cause the thyroid to underproduce thyroid hormones which over time can cause symptoms such as —

  • Goiter

  • Fatigue

  • Joint pain

  • Muscle aches

  • Constipation

  • Dry skin

  • Weight gain

  • Hair loss

  • Brittle nails

  • Mood changes

  • Memory issues

  • Sensitivity to cold

  • Infertility

How The Thyroid Gland Works

A small gland in the brain, called the pituitary gland, secretes Thyroid Stimulating Hormone (TSH) when instructed by the Hypothalamus (also located in the brain). TSH is interpreted by the thyroid gland and in turn releases T4 and T3 hormones. T4 is an inactive form of the thyroid hormone, and is converted into either Reverse T3 (RT3) or into T3. That which is converted into RT3 remains inactive, while that which is converted into T3 becomes active and can begin to bind to cell receptors in your body to regulate cellular metabolism.

Functional Thyroid Testing at Carolina Holistic Health

Most conventional medicine doctors will focus on your TSH and possibly your T4/T3 levels when testing your thyroid, overlooking your body’s other factors that can influence your thyroid. You might even go to the doctor, have a thyroid test, and be told that everything looks “normal”, when in reality, there’s a lot more going on inside your body than meets the eye.

As part of our functional medicine approach here at Carolina Holistic Health, when we look at your thyroid levels, we test for several different biomarkers to make sure we’re looking at the bigger picture. You’ll also notice below that I’ve differentiated between functional range and conventional range. With functional range we’re looking at a more precise range that achieves your optimal health. The conventional range is what is recommended in traditional medicine, a less specialized and broader range.

Here are some of the biomarkers that we test for at Carolina Holistic Health and our optimal functional ranges vs the traditional conventional ranges.


As mentioned above, TSH is produced in the pituitary gland and stands for Thyroid Stimulating Hormone. It controls the production, storage, and release of thyroid hormones. Increased levels of TSH indicates the need for thyroid hormone, whereas decreased TSH indicates the body has a low need for thyroid hormone. Sometimes TSH levels can be quite misleading if the pituitary gland is not functioning optimally.

Functional Range: 1.5 - 2.5 mlU/L

Conventional Range: 0.4 - 4.5 mlU/L

Total T4

Thyroxine, also known as T4, is the storage form of thyroid hormones and is stimulated by TSH. When measuring total T4, it consists of the bound form and unbound form, which is usable by the body. Unless measured with T3 uptake, total T4 levels don’t give a clear picture of overall T4 activity.

Functional Range: 6.0 - 11.9 mcg/dL

Conventional Range: 4.5 - 12 mcg/dL

Free T4

Free T4 is the unbound form of T4. Less than 1% of circulating T4 is in the free form. Measurement of free T4 levels indicate the amount of active T4 hormone in the body. Low values of free T4 indicate hypothyroidism. This number may appear “normal” in the early stages of thyroid disease. Deficiencies of zinc, copper, vitamins A, B2, B3, B6, and C can also cause this number to be lower.

Functional Range: 1.0 - 1.5 ng/dL

Conventional Range: 0.8 - 1.8 ng/dL

T3 Uptake

This biomarker is used to measure the binding capacity of thyroid hormone. It’s helpful in confirmation of whether or not T4 levels are actually elevated. T3 uptake can also be used to indirectly measure activities of other hormones such as estrogen.

Functional Range: 27 - 35%

Conventional Range: 22 - 35%

Total T3

Triiodothyronine, known as T3, is an indicator of active thyroid hormones in the body. Total T3 is good for measuring if your body is able to convert T4 to T3. Conversion mostly happens in the liver, so healthy liver function is important for a healthy thyroid. There are also nutrient deficiencies that can influence conversion.

Functional Range: 90 - 168 ng/dL

Conventional Range: 76 -181 ng/dL

Free T3

As previously mentioned, T3 is the most active thyroid hormone. Free T3 measures the amount of T3 that is able to be absorbed by the body, which is about 8-10% of total T3. If this number is low, the body is not converting enough T4 into free T3, a common cause of hypothyroidism.

Functional Range: 3.0 - 3.5 pg/mL

Conventional Range: 2.3 - 4.0 pg/mL

Reverse T3

Reverse T3 is formed from T4 but is unusable for thyroid hormone functions. In fact, it actually slows down the metabolic processes of the body because it competes with the usable form of T3, free T3. There are many causes of increased reverse T3 levels such as high stress, chronic illness, unstable dieting, vitamin deficiencies, caloric restriction, lack of exercise, fasting, and increased alcohol intake.

Functional Range: 10 - 25 ng/dL

Conventional Range: 8 - 25 ng/dL

Thyroid Antibodies — Thyroid Peroxidase & Thyroglobulin Antibodies

Many thyroid conditions are autoimmune in origin and are the result of the body attacking its own thyroid cells. Hashimoto’s is an autoimmune disease that causes hypothyroidism. Graves disease is an autoimmune disorder that causes hyperthyroidism. When looking at a patient's thyroid, it's good to rule this component of thyroid disease in or out.

Thyroid Peroxidase (TPO) Ab Functional Range: 0 - 6.8 IU/mL

Thyroglobulin Ab Functional Range: 0 - 0.9 IU/mL

The Next Steps

In a traditional doctor’s office you might get your thyroid tested, discover that there’s an imbalance, and then get a prescription to “fix” your problem. But what does that type of treatment look like down the road? Do you have to keep taking that prescription for the rest of your life? With functional medicine we do look at your thyroid levels, but we also look at potential root causes of a thyroid imbalance. Our goal isn’t just to improve symptoms, instead we want to get to the root of the symptoms and help you find the best long term solution for you.

If you’re experiencing any of these symptoms and want to check your thyroid in the most functional way possible, click here to book your free 15-minute consultation with Dr. Stefanacci today!

Stay tuned for Part 2 of our Thyroid Series in which we explore some of the root causes that may lead to thyroid imbalances!

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