Thyroid UK
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Getting My FT3 back up again and what about RT3?

Such a lot of wisdom on this site--so glad to have found you because my Docs know next to nothing about Thyroid issues.

After two years on 100mcg Levo (2014-16) lost hair and 1/2 left eyebrow and gained weight I could not lose. Gym caused energy crashes which put me in bed for days at a time.

June/2016.. TSH .004.

FT4 1.3 (.7-1.8)

FT3 2.75 (2.3-4.2) RT4 20 (8-25). Seemed a problem converting T4 to FT3 so went to 90mg Armour but energy crashes and weight gain continued Then I started palps and 'hot head' symptoms.

Oct 2016 TSH <.004

FT4 1.0 (.7-1.8)

FT3 4.2 (2.3-4.2) RT4 14 (8-25)

I cut Armour to 45mg and a month later FT3 had plunged to 2.64 and I had god-awful insomnia and fatigue. I started iron supp. and digestive enzymes.

So now I am at 65 mg NatureThroid and today started adding 10mcg Cytomel with plans to increase it, if needed) after Jan 9 labs are drawn because in the past I felt best when T3 was high.

Any suggestions for me? Is the RT3 causing weight issues? Is it possible I might do best on T3 only?

Oh and a.m. Cortisol (blood) was 10.5 (4-22). Ferritin 56 (13-150) and Iron 66 (30-150) am supplementing to raise those last two.

12 Replies


Where you've posted RT4 do you mean FT4? You don't appear to have included any rT3 results.


Yes, that should be rt3 on same line as ft3. Is there a way I can edit that post?



Click on the v down arrow underneath your post and select edit.


Thanks, Clutter.



Results looked good to me on 90mg Armour. rT3 14 is mid-range. I can't see that can be causing any problems and I've never heard anyone say rT3 has anything to do with weight gain.

It was drastic reducing to 45mg. Hopefully you'll feel well on 65mg NatureThroid + 10mcg T3.

1 like

Yes, I hope. The Endo wanted me to go lower but I talked her into that Cytomel.

I read that rt3 puts your cells into a hibernation state so you can only gain. I think that's from Ben Wilson. So he advocates a t3 protocol to clear the rt3.



We all have rT3. T4 converts to T3 and rT3. rT3 is the body's brake on converting too much T3. If rT3 is going to be a problem it is only when it is over range.


This is an explanation re RT3 and go to the second question/a nswer:-


This is an excerpt which might be helpful re RT3;-

Old studies show that on average, most people convert more than 50% of their T4 to reverse T3; correspondingly, they convert less than 50% of T4 to the metabolically active hormone T3. And the levels of reverse T3 fluctuate up and down through the day. Because of this, I’m never confident of coming to a conclusion that someone has a problem with high reverse T3, not unless the person has had multiple measures of the reverse T3 over a 24-hour period. Like the TSH, free T4, free T3, reverse T3 levels vary dramatically every 30 minutes or so. Depending on when a person’s blood is drawn or saliva taken. Sometimes the levels will vary enough so that a clinician will give the patient a different diagnosis from the one that he or she would have given 30-minutes before or after the blood or saliva sample was taken.

So blood levels vary rapidly. Because of this, I don’t believe the reverse T3 or the other lab tests in general are very useful. However, I do believe the reverse T3 is useful under one circumstance: when we have enough measures to get averages over time, and when the levels are regularly way out of range. So, in my view, the reverse T3 can be useful, but I think its usefulness is limited, which is true of the TSH and other thyroid hormone levels. >>>


Thank you for the helpful references. I wondered if rt4 might explain why on Levo I could lose absolutely no weight on Weight Watchers but on Armor I could lose, albeit very slowly. Dr Lowe seems to diagree with Ben Wilson quite a bit and it may be W's science is wrong and yet many people seem to get results on a temp. raising t3 protocol which Wilson says clears out the factor which has put the body in a state of hibernation (which I seem to be in), and that is rt4.

Before trying a t3 protocol I am working to optimize my iron levels and digestive 'fire' and see if I can get rid of hypothyroid symptoms on a combined t4/t3.


Did you mean rT3 (rather than rt4 as you typed)?


Yes, it's a good idea to try T4/T3. Armour obviously raised your metabolism high enough and levothyroxine is a pro-hormone and has to convert to T3 but may not do so efficiently or dose may be too low. T3 is active and goes straight into receptor cells. Its work then begins and lasts between one to three days.

I did see a mention from Dr L about Dr Wilson's method and I'll see if I can find the link:-

Go to the date February 4, 2008.

Dr Lowe was also a researcher and scientist.


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