The T3 Uptake test does not directly measure thyroid hormone concentrations.Instead, it indirectly reflects changes in thyroid hormone-binding protein levels.

Remember when we learned that most of the T3 and T4 are bound up to proteins and only a very small percent of thyroid hormones are freely floating in the blood. The T3 Uptake test is really looking at those proteins.  Some patients may have a deficiency in those proteins the hormone attach to.

This is important to determine since that is how the body maintains a stable pool of thyroid hormones in the bloodstream. If you are deficient in these proteins, then existing thyroid hormone levels would be depleted quickly

In hyperthyroidism, there is more T4 in the bloodstream, so there are fewer protein binding sites on Thyroxine Binding Globulin (TBG) available. This correlates with a higher T3 Uptake level.

In hypothyroidism, or when there is an increased concentration of TBG, then there is less T4 available, or there are more binding sites on TBG available. This correlates with a lower T3 Uptake.

T3 Uptake helps determine if your symptoms are due to a problem with thyroid hormone production OR your body’s ability to utilize available thyroid hormones.

Normal reference ranges for T3 Uptake vary based on the lab performing the test, but a typical normal range is 24-39% for adults. Reference ranges vary even more for children, based on age.

Falling within the normal range for T3 Uptake typically indicates adequate binding capacity of thyroid-binding proteins and balanced thyroid hormone levels.

Even if enough hormones are being produced by your thyroid gland and your blood levels for T3 and T4 appear normal, your body might still struggle to utilize these hormones if the binding proteins aren't functioning properly. This test helps reveal if there's an issue with these binding proteins and provides another clue as to why you still have hypo and hyperthyroid symptoms even if your other lab results are falling within normal ranges.

Factors Affecting T3 Uptake

• Thyroid disorders such as hyperthyroidism or hypothyroidism.
• Liver disease, including cirrhosis, which affects the synthesis and metabolism of thyroid-binding proteins.
• Renal dysfunction, such as nephrotic syndrome, which can alter the clearance of thyroid hormones.
• Pregnancy and estrogen therapy, such as oral contraception or hormone replacement therapy, which increase thyroid-binding proteins and decrease T3 Uptake.
• Consuming foods with phytoestrogens, such as soybeans, flaxseeds, and lignans found in grains, and other foods.
• Exposure to xenoestrogens found in plastics, herbicides, epoxy resins, and more.
• Certain medications or drugs, such as opiates (found in narcotic prescription pain medications or opiate street drugs like heroin and fentanyl has become increasingly popular), tamoxifen, nicotinic acid, furosemide, nonsteroidal anti-inflammatories (like aspirin and ibuprofen), glucocorticoids (like prednisone), phenytoin, androgen therapy, heparin, and more.
• Chronic constipation, preventing the body from properly eliminating excess estrogen.
• It can also be in genetic conditions affecting thyroid hormone-binding proteins, such as TBG deficiency in newborns.

The goal here is to figure out what is causing your problem so you can correct it.

• Is it a poor diet with lack of nutrition leading to vitamin and mineral deficiencies?
• Is it a lack of sleep or exercise?
• Is it too much stress?
• Is it a chronic infection in the body being overlooked by your immune system? This infection can prevent the body from absorbing the critical nutrients in your food and place the body under tremendous stress.
• Is it too much caffeine or nicotine?
• Is it a medication you’re taking, toxins your body is being exposed to, or a hormone disruption?

Usually, it is a combination of more than one thing. Taking a systematic approach to improve your health is where you will be able to reverse the barriers preventing your thyroid (and your body) from expressing itself in a healthy way.

Next week, we will discuss lab tests that you can use to determine if your thyroid issue is caused by an autoimmune condition. You will find out how to know if your own immune system is attacking your thyroid? That is the most common type of thyroid disease, whether it is Hashimoto’s thyroiditis or Grave’s disease. If it is autoimmune, then it is usually just a matter of time before your immune system begins attacking other body parts as well if the immune system is not corrected.

Once the immune system starts misfiring towards one type of healthy tissue (in this case your thyroid), it will likely start misfiring at other healthy tissues (or may have already started). That is what happens when it attacks your joints or gut, such as in rheumatoid arthritis, celiac disease, ulcerative colitis, Crohn’s disease, and so many other autoimmune diseases.

What is even worse, is once the immune system is misfiring and busy attacking healthy cells, it won't be busy attacking what it is supposed to attack like chronic infections the immune system is no longer paying attention to. These infections can be caused by parasites, bacteria, fungi, viruses, mold. It also will not be attacking the unhealthy cells that could turn into cancer. This zaps you of all your energy, leads to chronic inflammation and pain, and can ultimately put you at increased risk for developing cancer (like I did).

I am excited to share this with you because I believe if I had learned this information 20 or 30 years ago when my thyroid problems were still early, I could have course-corrected and avoided my thyroid cancer and helped remove barriers that were preventing my thyroid from healing. I could have avoided many other autoimmune diseases I developed as well and avoided a lifetime of hormone replacement as a result of having my thyroid removed. This is why I do this. I want to help YOU avoid what I went through.

I would love to hear back from you if you have any questions and to know if this information is helping you better understand your thyroid.

Feel free to check back on the previous videos in the series here.

Find the extensive list of symptoms in this document hand out here: Common Signs and Symptoms of Hyper and Hypothyroidism.

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