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Thyroid UK
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Does anyone NOT have a conversion issue, but still have low FT3??

Hi All:

Has anyone experienced "in range" FT4 and low FT3, without a high rT3, aka conversion issue? I'm trying to develop my argument to ask my doc to try me on t3 only. I'm having conversion issues, most likely related to the low iron and or adrenals. He won't give me IV iron, though I seriously need it. So I'm trying to handle the iron on my own. Meanwhile I need to get my t3 case together for my next appointment. This NDT isn't working. 8 weeks into meds,I'm certain I shouldn't be getting worse.

Thoughts? Experience?

Thank you all for your time.....

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If you have low TSH, high FT4 and low FT3 while on Levothyroxine only it indicates poor conversion.

Are you optimally dosed on NDT ie low TSH, low-mid range FT4 and FT3 in the upper 3rd of range? Nothing will work if you are undermedicated.

Sometimes it is also necessary to try several brands of NDT before you find one which suits you.


Thank you Clutter. I am going to switch to NP Thyroid in October at my next doc appointment. Right now I'm no different than I was when I started really:

(After 7 weeks on Nature Throid. At time of bloods, taking 1.25g)

TSH 1.67 (.45 - 4.5)

FT3 2.4 (2.0 - 4.4)

rT3 12.5 (9.2 - 24.1)

FT4 .9 (.82 - 1.77)

TPOab 11 (0 - 34)

Tgab <1 (.0 - .9)

Vit D 54.2 (30 - 100)

SHBG 108.2 (24.6 - 122.0)

DHEA 280.1 (57.3 - 279.2)

Prolactin. 12.5 (4.8 - 23.3)

Ferritin 15 (15-150)

Iron serum 83 (27 - 159)

TIBC 312 (250 - 450)

UIBC 229 (131-425)

Iron Saturation 27 (15-55)

I was thinking about adding t3 to the NDT; but I'm going to wait until it's time to titrate up to 2.5g as today was my first day on 2g. So maybe I've got to give it more time? My FT4 has gone down but I thought that that is to be expected on NDT?



You were mildly undermedicated on 1.25 grains. You should stick with 2 grains for 6-8 weeks and retest before increasing further or adding T3.


Symptoms can lag behind good biochemistry for several months.


Thank you Clutter! You know when I took the first dose at 2g, yesterday, I actually thought about you and greygoose ! 'Cause I remember you mentioning that before that once one gets to 2g. They should slow down the titrate....I use so many thoughts from you and other members to help me through and just encourage myself with your words. You all really have been a true and reliable source and strangers or not, I have love and respect for you. Thank you. So much...


Thank you so much- I just needed that reassurance, and I appreciate it. Very much. The time seems to move so slowly when you're titrating like I did (1/4 per titrate), and when you're so new to this and the symptoms are unrelenting.

I get nervous when I don't see any improvement. The hormone is such a different ballgame than traditional "medicine". Cognitively I knew, "ok im not even up to 2g yet..." but In that time, I've read so much that I start to overthink and wonder, "ok im not doing any better so am I not absorbing? Am I converting? And I too high in rT3?" -- essentially wondering about and prematurely applying all the things I'm learning, then theorizing that that's why I'm still struggling - when I haven't even gotten to a dose high enough to consider those advanced issues.

Yesterday the pain and swelling were just agonizing, as I've had it now for several weeks. So it gets really hard to hang in there. Reminding me of the 6-8 week lab wait after 2g mark, helps me stay focused and patient (I was sooooo about to just titrate back down to zero!). I really appreciate the wisdom you all share bc it gives me a cognitive and objective look at everything. A peace of mind even during these tough times.

I bet a lot of people probably give up before they get to a therapeutic dose, but it's so easy to see why they do.

I was really really down yesterday - so thank you for being a lighthouse. Thank you...



Has the pain and swelling has not improved at all since you've been titrating NDT? I would have expected some improvement as your levels weren't very low on 1.25 grains.

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Well the eye pain (I had pain behind the eyes, and blurred vision) - that has improved.

The swelling unfortunately, in my legs, face, and abdomen have not. I also have the hallmark, of elevated creatine kinase. All of this happened in close time with the other symptoms that first made me look into thyroid testing.

I went to a rheumatologist but he never said or did anything other than write on my results, "you're creatine kinase is elevated. Please see Dr Ro,$:&" - well my endo didn't do or say anything and while the swelling is visible and the heaviness of the tissue is there, he just looked at my legs and said to try to elevate them every night and continue wearing compression stockings.

This isn't fluid from typical swelling. In some parts it's pitting in most parts it is not.

Even the connective tissue across the tops of both feet, are effected. There is a line that extends horizontally across both feet, above the line, up to the toes, the skin is lighter, and below the line all the way to the ankles it's darker, almost a bruised look.

My face and arms are puffy as well. My face looks like I've objected water into the cheeks.


I don't think you should equate conversion problems and rT3. You get high rT3 when you have a conversion problem, and keep increasing your T4 to try and get enough T3. Once your FT4 gets to a certain point, it will convert into rT3 because you have too much unconverted T4 in your system. RT3 doesn't cause a conversion problem.

Your problem is under-medication. So, increasing your NDT should raise your FT3 and make you feel better. It is normal to have low FT4 when taking T3, but your FT3 would be higher if you were on the right dose. I'm not convinced adding T3 is necessary at this point. :)


Hi Greygoose! Thank you....I see what you're saying. I never knew that, but when I (I'm a nerd, and draw out everything) drew out the systems yesterday I looked at the breakdown of FT3 against rT3 and wondered does "rT3 actually represent a bad thing, when there is enough FT3?" So you're explanation speaks directly to that thought....thank you.

Thought/question just for learning sake: if my FT3 does NOT improve but the rT3 continues to rise, that's when you would consider the t3 addition?

Have you ever experienced of heard of someone's FT3 AND rT3 going up? is that possible?

I hope this 2g world shows me some improvement! Then I'll be on my way! I bought some desiccated liver yeasterday to help my pathetic ferritin level....so I'm working all angles! πŸ˜‰


'Have you ever experienced of heard of someone's FT3 AND rT3 going up? is that possible?'

Personally, I've never had my rT3 tested. This is just what I've gleaned from what I've read. RT3 is nature's way of stopping T3 from getting too high. So, no, I don't really think that would happen.

'Thought/question just for learning sake: if my FT3 does NOT improve but the rT3 continues to rise, that's when you would consider the t3 addition?'

I don't really think rT3 comes into that equation at all. RT3 can be raised because you are unwell, or starving, in which case you don't want your FT3 to rise because you're trying to conserve energy. It's time to add in T3 when your FT4 is right at the top of the range, and your FT3 is struggling to reach mid-range, meaning that you have a conversion problem. That excess unconverted T4 will then convert to rT3 so as not to waste the T4 - because, hopefully, the rT3 will then go on to be converted to T2. That's roughly what happens, anyway.


Ahhh. Provacative.

'RT3 can be raised because you are unwell, or starving, in which case you don't want your FT3 to rise because you're trying to conserve energy. '

I have read that people who have autoimmune disease aside from thyroid concerns, like Type 1 diabetes, what I have, will have an elevated rT3. So that's another cause of my confusion, because my rT3 at initial Hashimotos diagnoses was elevated 23.5 (9.2 - 24.1), with a perisitently low FT3 2.1(2.0 - 4.4).

So in my case, I assume my symptoms were/are from this low FT3. But like you mentioned, the elevated rT3 is to protect me and thus, keeps the FT3 low. It's a vicious cycle. I believe the diabetes, for many, myself included, will keep the rT3 elevated as Type 1 is degenerative in nature and with age, degenerates the system. I am interested in what continued external t3 from the NDT will do. I expect, and hope, that it will lower the rT3 and increase the FT3, ultimately giving me some semblance of relief.

Thank you - because this thinking on rT3, gives me a fuller analysis of what's happening and how to address it.


No, the rT3 doesn't, in and of itself, keep the T3 low. rT3 doesn't do anything, it's totally inactive. That's just the way it works : more T4 is converted to rT3 that T3 to conserve energy.

The NDT will raise your FT3, but whether or not it will lower your rT3 remains to be seen. It depends what's causing the high rT3.

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Ahhh. I see. I have read that before that the reason the rT3 is elevated differs from person to person. It is very common in Type 1 diabetic women who've had the disease for more than 20 years. I've had it all of my life - 33 years. I don't suspect I'll be able to get it down permamnently.

I was prescribed LDN at my request, but I stopped taking it as my new doc thinks it will over suppress my immunity. I don't believe that. I may start taking it again and take it long enough to see if it helps. i know some believe gluten free diet will help. But I'm very covinced my rT3 is Type 1 diabetes related.


It could well be. But, I'm not sure that either LDN or gluten-free is going to lower your rT3.

But, there is no proof that your rT3 is doing you any harm, or is in any way responsible for your symptoms. I tend to regard rT3 as a bit of a red herring, myself.

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Ahhh. I understand what you mean. I sure am hoping on this FT3 goes up....I wouldn't even care about rT3 if my FT3 would stop being such a jerk! πŸ˜‰


I'm sure it will, given time. :)

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