Is there any scientific evidence showing that T... - Thyroid UK

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Is there any scientific evidence showing that TSH is often suppressed when taking T3?

TaraJR profile image
11 Replies

Patients taking T3 know that their TSH is very often suppressed. Some doctors seem to accept this is ok, if T4 and T3 are not too high/over range.

But - does anyone know of any studies showing this does happen? It would be great to have something to quote back to doctors who don't accept it.

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TaraJR profile image
TaraJR
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jimh111 profile image
jimh111

It depends on dose onlinelibrary.wiley.com/doi... .

guysgrams profile image
guysgrams in reply tojimh111

Unfortunately there is nothing current as far as articles go. They need to be updated. Sad that there are not new studies taking place.

jimh111 profile image
jimh111 in reply toguysgrams

The study is good and so valid. However, I suspect many people who need T3 have a pituitary that is underperforming and so their TSH falls more quickly. There is evidence that TSH stimulates deiodinase, so a subnormal TSH would lead to a need for T3.

guysgrams profile image
guysgrams in reply tojimh111

I just know that when I was first put on T3 with just a small 5 mcg twice a day my TSH went to .01 and not changed even with a higher dose of T3. My thyroid is atrophied and no longer working at all.

TaraJR profile image
TaraJR in reply toguysgrams

Similar to me. I had RAI many years ago and mine is completely atrophied now. T3 has suppressed my TSH but T3 and T4 are well within range.

jimh111 profile image
jimh111 in reply toTaraJR

Do you know your TSH, fT3, fT4 from just before you started T3 and what dose of levothyroxine were you on?

jimh111 profile image
jimh111 in reply toguysgrams

Do you have your blood test results from before and after you started T3 and what doses of T3, T4 were you taking? What was your TSH just before you started T3?

guysgrams profile image
guysgrams in reply tojimh111

TSH was 2.293 and FT4 was over range @ 1.7 FT3 low in range @2.6. My TSH started fluctuating dramatically for the two previous years prior to this where in the past it was pretty stable. First introduced to T3 my TSH .011, FT4 1.67 and FT3 3.9. This was a sweet spot to be sure because my Endo had not lowered my dose of T4 when she added the T3 and all hell broke loose that fall. My FT4 went over range to 1.95 and my FT3 lowered to 3.4 but my RT3 was 60.2 and let me tell you I felt like death warmed over! I had to stop all T4 and slowly add T3 in to feel some sort of normal. It took 2 years of T3 only because when I would try to introduce T4 back in my RT3 would climb and go over range. Fast forward those 2 years and eventually I lowered my T3 and added the T4 back in. My dose now is 25mcg T3 and 75 mcg T4 (Tirosint). I've been on this dose since for 4 years now. My TSH has pretty much stayed at .01 since late 2015 when first introduced to T3.

jimh111 profile image
jimh111 in reply toguysgrams

It seems your thyroid went a bit bonkers around the time you started T3 as you wouldn't expect fT4 to go up. Your current dose is equivalent to about 150 mcg levothyroxine which isn't a big amount.

guysgrams profile image
guysgrams in reply tojimh111

It did prior to but after start of the added T3 it did go nuts because my Endo had not taken down the dose of T4 I was on.

McPammy profile image
McPammy

Not everyone has suppressed TSH on T3. I take combined treatment levothyroxine T4 and liothyronine T3. My TSH is always just about in range along with my T4 and T3 levels being in range. I feel symptom free.

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