Also called Reverse Triiodothyronine
The thyroid produces T4 (storage hormone), T3 (quick energy), T2, T1 and Calcitonin.
T4 converts to one of two things – T3, or Reverse T3.
Every cell in the human body depends on T3 for its energy making process and has T3 receptors.
How do you know if you have high rT3?
This Reverse T3 does NOT cross into the nucleus very well and does NOT compete with triiodothyronine for its receptors. When Reverse T3 (rT3) is high, we have symptoms of hypothyroidism. We usually see a low FT3 with high rT3, hence the symptoms.
This, however, can also be other things so this alone is not enough.
Thankfully there is a great lab test for this that is just rT3 or Reverse T3 or Reverse Triiodothyronine test. Often doctors are reluctant to test this as they are unfamiliar with what to do with results. We have found this test to be one of the most crucial as if it isn’t converting it isn’t working.
When interpreting this lab for USA, Europe and Canada you want your result to be NO MORE than 2 points above bottom of the range. Example if your lab range is 8-22 you would want your rT3 at 10 or less.
For Australia if your lab range is (140-540) you want this at 165 or less and if your lab range is (170-450) you want this at 196 or less.
Another gauge is if your FT4 is higher than mid-range Every cell in the human body depends on T3 for its energy making process and has T3 receptors.
The two biggest culprits behind RT3 are low iron and/or cortisol issues. We also often see high RT3 from too much T4 medicine or T4 only medicines.
Iron tests are:
- Serum Iron
- TIBC
- % Saturation
- Ferritin
A 24-hour saliva cortisol test should be ordered to check your cortisol levels at four different points during the day. It measures what’s free and available for cell use. This test is used to see if you have an HPA Axis Dysregulation. A blood serum test will not be accurate for this purpose, because it measures what’s bound by proteins and is used to diagnose adrenal insufficiency diseases. It takes approximately 8 days to receive the kit in the mail and another 5-10 to receive the results in an email. Please click here for our page with more informaiton regarding this test.
Another cause of rT3 is when doctors prescribe T4 in addition to NDT. This is simply too much T4 medicine for most people and we commonly see it causes an increase in RT3. Often doctors do this because they see a low T4 and are taught (in error) that T4 is the most important. Again, in theory if a person converted T4 to T3 this would work but in practice it simply does not work.
Some other reason could include:
- Anxiety
- Aging
- Bipolar Depression
- Cardiovascular disease
- Chronic and acute dieting
- Chronic Fatigue syndrome
- Chronic Infections
- Chronic Inflammation
- Depression
- Diabetes
- Fibromyalgia
- The genes DIO1 and DIO2 being activated
- Heavy Metal detox
- High cholesterol and triglyceride levels
- Insulin resistance
- Liver and Kidney disease
- Lyme Disease
- Some medications like beta blockers.
- Migraines
- Neurodegenerative diseases
- Physiologic stress and anxiety
What’s the fix? We have found that because rT3 comes from T4 not properly converting to T3 that lowering the amount of T4 (NDT contains T4 and T3) that’s being taken to 1-1/2 grains, or less, will help.
Some have found that supporting their liver with Dandelion Root or Milk Thistle helps.
Some add selenium but please be sure to test first as too much is as bad as too little.
Some replace the lowered amount of NDT with T3 to alleviate hypo symptoms. Please note, adding T3 does not lower rT3, it simply provides the hormone your body needs to be healthy.
Also please note that rT3 and Pooling (for lack of a term, as Pooling is not a medical term) are not the same thing. Please refer to our Pooling page for more info.
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Some ask if they can increase their NDT as soon as the rT3 goes down. We have found this to be a mistake as rT3 will come back if the cause was not addressed. Be sure to find and address the cause or it will happen again.
The Reverse T3 section on this site is very good info: https://www.nahypothyroidism.org/thyroid-hormone-transport/print/?fbclid=IwAR2Sf1cR1fELuRhhQPxZkS-eYMaFZsSVmBqyHHrFfxBPQ4luyCJlhgTXcZs