Is t3 resistance real?

[Ralph1985]

I was researching cytomel as I have some at hand and was planning on adding a bit to my synthroid but now I’m confused as I have found various doctors recommending against it because you can down regulate your t3 receptors by using extra t3 and so making your symptoms worse. Is t3 resistance a real thing and has anyone here experience it?

[helvella Administrator Thyroid UK]

I'd be cautious of following any doctor who explains it like that.

Just what do they think happens in people with hyperthyroidism? Sometimes they have astronomic levels of T3. The inference I take is that they would be prime cadidates for suffering T3 resistance. Not in the least convinced that is true.

Yes, there is Thyroid Hormone Resistance (often now called Impaired Sensitivity to Thyroid Hormone) or Refetoff syndrome.

jimh111 is probably one of the most aware memebers and I hope he has time to respond.

[Ralph1985 in reply to helvella]

Indeed I’m aware that I can’t trust all doctors and what you said about hyperthyroidism than would be causing t3 resistance makes sense. the thing is they explain this theory in a way that would sound very convincing, at least to me. I saw it on YouTube! And it wasn’t just one doctor with one video there’s actually a couple pushing this around. I do hope someone can explain refetoff syndrome and how is developed.

[helvella Administrator Thyroid UK in reply to Ralph1985]

Maybe have a look here:

pubmed.ncbi.nlm.nih.gov/259...

The second author is Samuel Refetoff.

[Hillwoman in reply to Ralph1985]

Refetoff's Syndrome is restricted to certain genetic forms of TH resistance and it usually manifests in infancy, often with devastating effects. Read about it here: thyroidmanager.org/

Probably rather more people with resistance problems have peripheral resistance, which the late Dr John Lowe wrote about. shaws has a number of links to his archived website that you may find useful. PR has unknown origins, but it's possible that it can be a consequence of toxic exposure, poor blood glucose regulation/insulin resistance - just as two examples.

[helvella Administrator Thyroid UK in reply to Hillwoman]

I collected much of Dr Lowe's website into a PDF as other means of access have become awkward:

dropbox.com/s/w7cjut689r1w1...

[Hillwoman in reply to helvella]

Brilliant! Thank you. I lost my links when my old laptop died and the backup failed.

[helvella Administrator Thyroid UK in reply to Hillwoman]

If I find more, I shall add to that PDF - so do check back.

[jimh111 in reply to Hillwoman]

There are forms of peripheral resistance to thyroid hormone caused by endocrine disrupting chemicals, they disrupt the binding of thyroid hormone in peripheral tissues but not in the pituitary. I call this ‘Acquired Resistance to Thyroid Hormone (ARTH)’to distinguish it from the genetic forms.

[jimh111]

Hormone receptors can be blunted by high levels of hormones but these have to be very high. This is a recognised problem in toxicology testing where the doses used are exceptionally high (in animals to find fatal doses and check for cancer). These exceptionally high doses can reduce expression of receptors (how many) and receptor response. I don't know for sure but I don't think patients normally experience these very high levels, they are orders of magnitude above normal levels.

High thyroid hormone levels that suppress TSH can down-regulate the hypothalamic pituitary thyroid axis, the patient ends up with a TSH that is lower than you would expect it to be for given fT3, fT4 levels. The problem with this is the low TSH reduces T4 to T3 conversion and scares doctors. This is why I encourage patients to try and get better without pushing their TSH down if they can. Of course some of us need high thyroid hormone levels that result in a very low TSH.

[jimh111]

I forgot to mention that if all T3 receptors we’re down-regulated it would affect pituitary T3 receptors and the pituitary would pump out masses of TSH. It is possible that the pituitary might be more robust and not so sensitive to extreme thyrotoxicity, this would be an evolutionary advantage. Even so, I think hormone levels would need to be extraordinarily high to blunt receptors. If this happened in real life there would be known cases reported in the literature.

[Hillwoman in reply to jimh111]

Very important points.

[jgelliss in reply to jimh111]

Great insights jimh111. Thank You . From my personal experience . After my TT being on T4 only was dismal to put it mildly . Switching from Synthroid that has allergic fillers in them to a another thyroid med with much less fillers and adding some T3/NDT made a huge difference for me . T3 is the active and fast acting thyroid hormone that our heart brain etc. have receptor sights for . Being a poor thyroid converter T4 to T3 . Adding some T3/NDT with a lowered T4 dose was a no brainer .

That took years of a lot of perseverance.

[Ralph1985]

Great answer, very informative thanks for replying everyone

[DippyDame]

Without labs and ranges it is difficult to understand why you might wish to add T3

.

Do you have high FT4 and low FT3?

Do you have a problem with converting T4 to T3?

Are your folate, ferritin, vit D and vit B12 levels optimal, this is essential to support adequate conversion.

Taking T3 without a good reason is not a wise move. It is a potent hormone and must be treated with respect....just "having some to hand" doesn't seem a sound reason.

Medic's knowledge of thyroid disease is frequently limited and most endos are diabetes specialists.........that's why over 100,000 patients have arrived here looking for advice! Not every patient responds to levothyroxine.

By "T3 resistance" are you referring to Thyroid Hormone Resistance ...same thing different name!

I have RTH and take a huge dose of T3 which consequently suppresses TSH and FT4.

That supraphysiological dose acts as a "battering ram" against the cellular resistance, and when the dose is high enough that "push" enables some of the availableT3 to overcome the resistance and to enter the cells where it can do what is required of it. The T3 left in the blood will eventually be excreted by bladder or bowel. FT3 will, therefore, be elevated, however it is the T3 that enters the cells that is important - that cannot be measured so we have to dose by specific symptoms

Clearly not a scientific explanation,

On the other hand, if the patient is hypo but doesn't have RTH then taking too much T3 will result in overmedication with the associated symptoms.

I wonder if this is what your medic fears.

RTH is a genetic disorder, as yet much more research is required. There is also a theory that endocrine disrupting chemicals may be responsible. It gets complicated!

Low T3, for whatever reason and for however long, will, as I understand it, cause receptors to become inactive. Correct medication should reverse this.

I'm obviously not a medic just another patient who has had to read and learn their way to improved health! I'm sure others will pop up with more knowledgeable responses.

Apologies if this is not the "take" you hoped for.

Best...

DD

[Ralph1985]

I started 170 mcg of synthroid on the 8th this month a doc wants blood work in 3 months. I asked him once a while back about t3 and ndt and he was really against those. He’s a type that only like t4 and says that it’s normal for us with hypothyroidism to feel “blah” most of the time. I do have time where my hashis flare up last time I had a tsh of 2.80 and my ft3 was .459 over the top as the top range was .450 so I thought it was a mini flare up as I had this tsh leves before and my ft3 been in the dumps. Anyways I was thinking that maybe I should add 5mcg if cytomel to my synthroid.. I heard 5mcg of t3 isn’t much.

[jgelliss in reply to Ralph1985]

5 mcg of Cytomel can be much if you need less . Adrenals will let you know . It's a very powerful thyroid hormone . It's fast acting unlike the T4 Levo thyroid med that is slower acting . The best is always journal your symptoms those are your cellular results .And compare your FT3 FT4 TSH lab results to your symptoms . It is very telling .

[penny]

When you ask ‘is it real?’ Do you mean, is it imagined?

[Ralph1985]

No, I mean is it something that is true and can happen, this doctor was saying if you take t3 you will be bombarding your t3 receptors with a lot of the hormone and cause t3 resistance, he kind of completed to insulin resistance. He said if we have too much t3 as to take in by supplement and not being converted by t4 as we we need it. All that t3 from t3 medication in our blood all the time will cause a form to t3 resistance just like insulting resistance would happen.

[DippyDame in reply to Ralph1985]

Too much T3 will cause symptoms of overmedication which you would soon be aware of!

I don't think this medic has much idea about either T3 or Thyroid Hormone Resistance. He seems confused and unfortunately that will leave his patients confused too.

I guess, by his language, that he is a diabetes specialist and poorly informed about thyroid disease.....not unusual I'm afraid.