Instead of taking a standard thyroid stimulating hormone test, you should have your reverse t3 (rT3) levels checked instead. rT3 levels prove to be a more accurate indicator for cellular hypothyroidism when there is a malfunction in thyroid hormone transport.
Taking a TSH may not be enough, but a reverse T3 test will be more accurate in diagnosing any thyroid disorders you may have.
Reverse T3 And Thyroid Hormone Transport
1. Cellular Activity
Biological activity happens when T4 and T3 cross the cellular membrane from the serum into the target cells. This transport process has an important influence on the regulation of biological activity of the thyroid hormones.
— blood-test.co.uk (@BloodTestUK) January 12, 2017
The serum thyroid levels created by this transport are commonly used as an indication of cellular thyroid activity.
2. Energy Requiring Active Transport
There is a common misconception that the uptake of thyroid hormones into the cells is done through diffusion, when in fact is a form of energy requiring transport.
— BLK Hospital (@BLK_Hospital) January 21, 2017
Along with this discovery, was the knowledge that the rate-limiting step in the determination of thyroid activity is the rate of thyroid hormone transport into the cell.
3. Reduced Energy and Transport
Because the transport of thyroid hormones into the cell is energy dependent, any condition associated with reduced production of the cellular energy, such as mitochondrial dysfunction, will also be associated with reduced transport of thyroid into the cell.
— touchENDOCRINOLOGY (@touchENDOCRINE) May 3, 2017
Other conditions that can cause this cellular hypothyroidism are insulin resistance, diabetes, obesity, depression, chronic dieting, migraines, aging, cardiovascular disease, and physiological stress and anxiety.
4. Artificial Elevation of Thyroid Levels
The reduced thyroid transport seen with those conditions results in an artificial elevation in serum thyroid levels, especially T4. This makes the thyroid stimulating hormone test a poorer marker for tissue thyroid levels.
— BLK Hospital (@BLK_Hospital) January 20, 2017
5. T3 and T4 Transporters
Thyroid function testing– TSH levels and free T3 and T4 levels(need carrier protein to transport)
Goiter- increased thyroid gland size
— Mark Gurga (@KingsRansom21) December 17, 2010
There are different transporters specific and necessary for the transport of T4 and T3 into the cell where they have their effect. The transporter for T4 is much more energy dependent than the transporter for T3.
Even slight reductions in cellular energy result in dramatic declines in the uptake of T4 while the uptake of T3 is much less affected.
6. The Pituitary has Different Transporters
— Alyssa Tait (@AlyssaTait1) February 13, 2015
Thyroid stimulating hormone (TSH) tests usually don’t detect cellular hypothyroidism because the pituitary has completely different transporters that are not energy dependent. It also has an increased transport activity even while the rest of the body has impaired thyroid transport. This is because its transporters maintain or increase the uptake of T4 and T3 in low energy states.
7. Reverse T3 Levels are a More Accurate Marker
Has your doctor checked your reverse T3 levels? Find out why it’s important. https://t.co/lwC1EMDBUV
— NAH (@NAHypothyroid) March 7, 2017
Reverse T3 is an excellent marker for reduced cellular T4 and T3 levels not detected by TSH or serum T4 and T3 levels. Increased rT3 is a marker for reduced uptake of T4 and reduced T4 to T3 conversion. This means that any increase in rT3 is not only an indicator of tissue hypothyroidism but also signify that T4 only replacement would not be an optimal treatment.
The transporter for reverse T3 is similar to T4 in that it is energy dependent and has the same kinetics as the T4 transporter. This property makes it the most useful indicator of diminished transport of T4 into the cell.
Watch this video from Dr. Travis J. Elliot to find out more about the importance of reverse T3 levels!
The activity of these transport processes has an important influence on the regulation of biological activity of thyroid hormones. Thyroid hormone transport is an extremely important topic in order for you to have a more accurate evaluation of your thyroid’s condition. The most important determinant of thyroid activity is the intracellular level of reverse T3, and the most important determinant of the intracellular rT3 level is the activity of the cellular thyroid transporters.
Have you had a reverse T3 test? Share your experience with us in the comments below!