Low FT4 and High FT3 ???

[Meg1751]

18 yr old female with Hypo symptoms (fatigue, joint pain, brain fog/mood swings, weight gain - recently has gotten, hence the testing) and family history of Hypothyroidism

Not on any medication or vitamins. Cholesterol tested and good.

Test Results

FT4 0.7 (0.7-1.5 ng/dL)

FT3 3.8 (1.7-3.7 pg/mL)

TSH 1.77 (0.4-4.5 mcIU/mL)

Tg <20 (0-20 IU/mL)

TPO <10 (0-35 IU/mL)

TGI 0.095 (0.0-0.09 IU/L)

Repeated tests 4 weeks later with same results (1st time FT4 was at 0.8 and TSH was at 1.7, others had same numbers)

Dr did not want to give me T4 meds because FT3 high... so repeated blood work.

Going back to Dr in 2 weeks. After reading I will ask for Vitamin testing.

Any ideas of possible situation/problem?

[jimh111]

It would be worth asking your doctor to check your iodine levels as in cases of low iodine the body produces more T3 and less T4.

[Meg1751 in reply to jimh111]

Thanks!!! Good idea! I will put that on my list... really appreciate the help!

[DippyDame in reply to jimh111]

Just a thought jimh111 ...

Is there any indication here of some form of RTH?

Can we be sure thyroid function hasn't already been deteriorating before this test?

With said slightly elevated TSH , FT4 should be higher?

Yet, FT3 is high despite low FT4 ...why?

Can't be a conversion issue....or can it?

Low nutrients?

Did the FT3 slowly built up in serum over a long period....despite compromised conversion?

FT3 building up at serum level but not reaching cellular level/tissues?

"Abnormal" receptors?

Low tissue T3 despite high FT3

Supraphysiological dose of T3! Last resort.

Family history of hypo with hypo symptoms...labs don't fit hypo

This all sounds rather familiar!

I'm perhaps more drawn to look for the possibility after my own experience because I suspect RTH is more "common" than is recognised/acknowledged

My medics didn't have a clue either....for decades!

I found the answers here.

Sorry this a ramble but I suspect you can set me straight....

Think I'll risk egg on face and hit send!

Hope the OP improves soon.....

Best...

DD

[Meg1751 in reply to DippyDame]

Thanks- I had to look all that stuff up😂.

Not sure if I have indications of RTH, other than Hypo symptoms and higher FT3.. will talk to dr about that (he did think low end FT4 and high end FT3 was “weird”... and hence the blood retest )

Definitely possible thyroid function could have been deteriorating before now... guess looking back I had mild symptoms but in the past year it’s gotten much worse.

I’m sure I’ll have more test to run.

Thanks for the help... like to go in to Dr knowing what questions to ask!!!

[jimh111 in reply to DippyDame]

Will reply lower down so it isn't lost or out of sync.

[DippyDame in reply to jimh111]

Thank you!

[SlowDragon Administrator]

For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also EXTREMELY important to test vitamin D, folate, ferritin and B12

Low vitamin levels are extremely common, especially if you have autoimmune thyroid disease (Hashimoto's) diagnosed by raised Thyroid antibodies

Your TG antibodies test as high /positive

Ask GP to test vitamin levels

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

Private tests are available as NHS currently rarely tests all relevant vitamins

List of private testing options

thyroiduk.org/getting-a-dia...

Medichecks - JUST vitamin testing including folate - DIY finger prick test

medichecks.com/products/nut...

Medichecks often have special offers, if order on Thursdays

[Jazzw]

It’s not obviously a thyroid issue (at least, there’s not a lot of evidence yet... it may appear in a future blood test).

But I think I’d now be asking for my iron status, Vit B12/folate and Vit D levels to be checked out, given the symptoms you’re describing.

[jimh111]

I think you need to take a methodical approach as there are many possibilities.

The most obvious is iodine deficiency as this leads to more T3 less T4.

Sometimes the assays simply give the wrong result but this is very unlikely as your TSH is consistent with your unusual fT3, fT4.

Autoimmune hypothyrodism is unlikely as your TPO and TBG are low. There could still be thyroiditis (inflammation of the thyroid) which is causing excess T3 release but perhaps we would expect more T4 as well.

Lots of organs convert T4 to T3 often in small amounts. Sometimes organs such as ovaries can become diseased and their conversion goes into overdrive, they pump out T3. This is unlikely due to your young age but it would be a good idea for your doctor to do a general check up. Is the unusual T3, T4 causing your symptoms or is it due to another problem that causes unusual T3, T4 levels?

I don't think it is an RTH problem as they don't present with elevated T3 low T4. Family doctors and most endocrinologists don't have knowledge in this area so it's not worth raising the question.

I would check iodine levels and make sure there's nothing else going on. Then if you get nowhere ask for some levothyroxine to see how you respond, you may find the fT3 comes down which would alay your doctor's concerns about the high fT3.

[Meg1751 in reply to jimh111]

This is definitely going to be a methodical long road... my dr is an Endo though, not a GP. Guess we both thought first set of blood tests could be wrong... Did ask him for Levothyroxine before retest ... but he didn’t want to right now with FT3 values...

I’m guessing it’s going to be Vitamin and Iodine testing, and Ultrasound (mom has Hashis w/o antibodies - took other Endos a long time to figure out)

Why do you think it’s low iodine, besides for blood values... I live it States and most all Web info sites say we get enough salt And blah blah blah?? Or are you suggesting I have could have a problem processing that salt/iodine...

Thanks!!!

[jimh111 in reply to Meg1751]

I'd forgotten the US has iodised salt. Low iodine is common in most countries and it presents with low T4 higher T3. As it's very easy to check it's the obvious step forward, if only to eliminate the possibility. It could be thyroiditis and the ultrasound would help you find out. It's just a matter of doing the obvious and easy checks first.

Note I am a patient not a doctor.