'Subclinical Hyperthyroidism' - with normal FT4 and Ft3? Don't Know What to Think...

[clethe]

I was diagnosed in 2012 with Hashi's Hypothyroidism and struggled for over a decade to get an Endo who would work with my persistent low FT3. Unfortunately, my (sharp young bright female) Endo who understood that a low TSH is normal with combination therapy has moved away. I have been given to new young male Endo who has glowing patient reviews. However, in addition to the usual TSH FT4 FT3, he has today ordered three new tests that look for Hyperthyroidism. Why?

Since I have not yet met him, I don't know if this is just 'due diligence' for a new patient - or something else. Appointment is April 1st, so labs will be done a week or so prior. I always follow the same forum recommended protocol for labs and also stop Biotin 5 days before.

My lab results have been fairly consistent for awhile, tho it wouldn't hurt to have both FT4 and FT3 a bit higher. The FT4 in particular is sagging a bit and I feel some hypo symptoms setting back in.

These are the tests he ordered today. I've never had #3-5. What to expect?

1. Free Thyroxine + T4

2. T3 (Triiodothyronine), Free

3. Thyroid Stimulating Immunoglobulin (TSI)

4. Thyrotropin Receptor Antibody, Serum (TBII)

5. TSH reflex to T4F

Recent Labs:

2025-1-13 (100mcg Levothyroxine, 20mcg Liothyronine)

TSH 0.005 (.45-4.50)

FT4 1.41 (.82-1.77) 62.1%

FT3 3.00 (2.0-4.4) 41.7%

2024-10-9 (88mcg Tirosint-SOL, 20mcg Liothyronine)

TSH 0.006 (.45 - 4.50) 

FT4 1.43 (.82 - 1.77) 64.2%

FT3 3.4 (2.0 - 4.4) 58.3%

2024-7-30 (100mcg Synthroid, 20mcg Liothyronine)

TSH 0.005 (.45 - 4.50) 

FT4 1.46 (.82 - 1.77) 67.4%

FT3 3.30 (2.0 - 4.4) 54.2%

[greygoose]

Looks like this new young bright spark doesn't know that taking T3 suppresses the TSH! 🤣

[clethe in reply to greygoose]

UGH! Wondering if my previous well-informed Dr left partly because she wasn't following 'protocol' 🤨

[greygoose in reply to clethe]

Well, she wasn't that well-informed, leaving you with that low FT3 for such a long time.

[clethe in reply to greygoose]

Sorry I wasn't clear. The doctors before her for years kept me under-medicated. She helped me get my FT3 up to where it is now by prescribing Liothyronine - and ignoring the 'all-mighty' TSH. She did mis-step while ramping up the T3 - she thought the T4 had to be reduced. That backfired in a big way! Had to then re-ramp up the T4 while not reducing the T3. That was the ticket!

[greygoose in reply to clethe]

Yes, they all think that - I guess that's what they're taught in med school. And sometimes it's necessary. But not every time - especially given that taking T3 is going to reduce the FT4 anyway.

[DippyDame]

btf-thyroid.org/subclinical...

Well you won't have HYPERthyroidism if your FT3 is only 41.7% through the ref range! FT3 would be over range!

I wonder if that (suspected) diagnosis was based on a test carried out during a Hashi's hyper swing when Frees are temporarily raised....do you have those diagnostic labs?

As you say your labs are fairly consistent ( for a Hashi patient)

With HYPOthyroidism we aim to have both Frees roughly approaching 75% through their respective ranges

Current dose -

100mcg Levothyroxine, 20mcg Liothyronine)

How long have you been taking this dose?

I'd suggest it might help to increase T3 to25mcg ....be aware that this will naturally lower both TSH and FT4

Medics often seem to imagine that T3 "self adjusts" according to the body's needs, and overlook the fact that many people have impaired thyroid function eg poor T4 to T3 conversion

In addition, it's vital to optimise vit D, vit B12, folate and ferritin to support thyroid function

Do you have lab results from the original diagnostic test, and later, before T3 was added to theT4?

FT3 is the most important number being the active thyroid hormone

For good health every cell in the body must be flooded with T3 by way if a constant and adequate supply

Low cellular T3 = poor health

[clethe in reply to DippyDame]

Thanks so much for your help. I've been on this dose since 2023 and even before that consistently low-range FT3. Original test was back in 2012 when TSH was 4.80 (.45-4.50), Thyroid Peroxidase (TPO) Ab 302 (0 − 34) all else normal, thyroid needle biopsy found Hashi's.

I agree that a small increase in T3 could help! But am now wary that he is going to use the low TSH to instead drop my T3 dose. Been there, done that. 🥴

He might think 'subclinical hyperthyrodism' is something that needs to be treated. There are 'medical' articles that promote that course for 'elderly' patients, which I am (72). I am trying not to be anticipating the worst from this new appointment, but those lab tests seem to be a flag. Of course, they should all come back negative for Hyper!

[DippyDame in reply to clethe]

Does he understand that TSH is a pituitary hormone and basically a signal to the thyroid to raise or lower the hormone levels it produces.

It's original purpose was to identify hypothyroidism....nothing more. But it was tweaked as a method of monitoring the dose and that set the cat amongst the pigeons

thyroidpatients.ca/2021/07/...

TSH of 4.8 indicates HYPOthyroidism

I still don't understand how you can be hyperthyroid with a low FT3

As I think you know low FT3 is hypo not hyper thyroid

Let's hope the new bright spark knows this!!

Dropping your T3 will make you feel worse!

Makes one question what med schools are teaching!

Good luck!

[clethe in reply to DippyDame]

Hoping that I'm being unnecessarily concerned about all this, but flags went up seeing those lab orders. Will update after April 1st appointment - thanks so much for everyone's thoughtful suggestions and reminders!

[tattybogle]

'sub clinical hyperthyroidism' , by definition, means TSH under range , while fT4 and fT3 are still within range .

Hyperthyroidism means TSH below range and fT4 /or fT3 are over range.

(you mention both in you post) .

3. Thyroid Stimulating Immunoglobulin (TSI) .... This is looking specifically for the 'stimulating' antibodies which cause thyroid to overproduce T4/T3 in graves disease.

4. Thyrotropin Receptor Antibody, Serum (TBII) .... This is another test looking for the same antibodies , but it includes other variations of that antibody which do not stimulate thyroid to overproduce T4/T3

5. TSH reflex to T4F ... this just means "test TSH ~ if it's over/ under range ~ then test fT4"

[clethe in reply to tattybogle]

Thank you for listing the test descriptions. It's the 'looking for' Hyper that is a worry. My labs should come back negative, but just having to anticipate another battle with a doctor is distressing. Time will tell.

[tattybogle in reply to clethe]

just so you are aware ~TSI and TBII tests if mildly positive don't exactly 'prove' hyperthyroidism . it is unlikely , but possible that your TBII/ TSI may be positive .

they just show that those antibodies are present , and in cases where T4/T3 are too high (in a patient who is not taking any thyroid hormone replacement ) then raised TSI / TBII show the cause of the raised T4/T3 is those antibodies .

there is a big overlap in which types of antibodies people have ...

thyroidpatients.ca/2020/04/...

.most of us won't know for sure if we have any TSI /TBII /TRab because they are not usually tested in hypo's , but there are a % of autoimmune hypo people who will have slightly raised TRab /TSI/ TBII tests without them being enough to cause that persons thyroid overproduce T4/T3. ( and in fact one form of TRab actually the 'blocking' form causes the opposite ie hypo ~ high TSh / low T4/T3 )

[clethe in reply to tattybogle]

Thanks for the link! Wondering how much of this "Spectrum of Thyroid Autoimmunity" my new Dr has learned. If my TSI /TBII labs are slightly elevated (no TRab at this point) the looming question is how Dr responds.

thyroidpatients.ca/2020/04/...

This might complicate matters:

"You may think you are a “pure” Hashimoto’s patient because all you’ve ever had tested is TPOAb and TGAb and you’re definitely hypothyroid. But later, as your hormone levels and/or TSH shift, you may eventually find out that you could actually be a combination Hashimoto’s + Graves patient, or you might become an Atrophic Thyroiditis patient."

[tattybogle in reply to clethe]

well it will be certainly be 'interesting' to see what he thinks if they are slightly positive ,although it's most likely he'll just be confused , but hey , you never know...... surely some of them must be interested enough to do some 'reading ' sometimes .

good luck

[clethe in reply to tattybogle]

👍