Normal TSH, but High FT4?

[MrMacast]

Hi everyone,

Despite two endocrinologists confirming my thyroid is 'normal', I'm experiencing symptoms of an overactive thyroid like sweating, anxiety, and weight issues. My recent blood tests show a TSH of 1.58 mIU/L (optimal) but an FT4 of 24.4 pmol/L, which the lab deems high. I've heard that reference ranges vary between labs?

Should I seek another opinion or is the lab being cautious? I've already undergone extensive testing including pituitary gland, vitamin levels, and diabetes checks. Any advice from those who've faced similar issues would be appreciated.

[pennyannie]

Hello MrMacast and welcome to the forum :

Have you had your thyroid antibodies run - it could be you are dealing with a thyroid Auto Immune disease - Hashimoto's - which presents with transient symptoms of ' hyper ' but that tend to go away by themselves without the need for any medication ?

On the blood test they would probably look like TPOab - Thyroid Peroxidase antibody - reading / range ?

and yes we need ranges as they can vary from lab to lab :

[MrMacast in reply to pennyannie]

I’ve had a full thyroid panel done and all results were normal, except the FT4. The TPOab result was 8.6 klU/L.

My FT4 result was 24.4 pmol/L, and their reference range is anything over 22 is “high” and anything over 30 is “very high”.

[pennyannie in reply to MrMacast]

Do you have a Free T3 result and range there please ?

Are your symptoms transient or do they feel as though they are increasing and building - with no let up ?

[MrMacast in reply to pennyannie]

Here are all of my results:

TSH

Result: 1.58 mlU/L (Optimal)

Lab Ranges:

Low: < 0.27

Normal: 0.27 - 1

Optimal: 1 - 2.5

Normal: 2.5 - 4.2

Abnormal: 4.2 - 10

High: > 10

FT4

Result: 24.4 pmol/L (High)

Lab Ranges:

Low: < 12

Optimal: 12 - 17

Normal: 17 - 22

High: 22 - 30

Very High: > 30

FT3

Result: 6.2 pmol/L (Normal)

Lab Ranges:

Low: < 3.1

Optimal: 3.1 - 5

Normal: 5 - 6.8

Abnormal: 6.8 - 10

Highly Abnormal: > 10

TPOAb

Result: 8.6 klU/L (Normal)

Lab Ranges:

Normal: < 34

High: > 34

T4

Result: 151 nmol/L (Normal)

Lab Ranges:

Low: < 66

Normal: 66 - 181

High: 181 - 300

TgAB

Result:12.2 kU/L (Normal)

Lab Ranges:

Normal: < 115

High: 115 - 300

Very grateful for you looking at these!

[MrMacast in reply to MrMacast]

I've also had HbA1c, Testosterone, CRP, Vitamin B9 and B12, Iron, Cholesterol, Liver, Vitamin D and Creatinine tests and they have all come back normal (B9 and B12 are lower end of normal, but not classed as deficient).

[pennyannie in reply to MrMacast]

As you detailed - lab ranges vary throughout the country and we need the actual ranges used in the lab where your blood test was undertaken.

The ranges are just that - the suggestion of a range drawn from the mean average of the population.

Your T4 looks a little high by most ranges - though I've seen T4 ranges with 25 being the top of the range :

Your T3 looks a little high - but still in most ranges -

and why we need the ranges that relate to the actual blood test results ;

Maybe you have a nodule on your thyroid causing erratic spikes in thyroid hormones - and maybe a thyroid scan could help rule this in or out -

but if your TSH, T3 and T4 are in the laboratory ranges where the blood test was undertaken - I doubt a scan will be readily suggested on the NHS at this point in time.

[MrMacast in reply to pennyannie]

I've been having regular thyroid tests and the results have been consistent since June 2022. I've also seen 2 endocrinologists and I think at least 1 of them checked around my thyroid area for lumps or bumps, etc.

I do have a very fast metabolism and I'm underweight, though I have always been underweight (I'm 30 next month). I don't mind seeing another endocrinologist, but I've seen 2 already and they are telling me there's no action needed on the results, yet my blood tests keep coming back with very similar results to the ones I posted above.

Would generally being underweight and having a fast metabolism cause higher FT4, rather than FT4 causing higher metabolism? I'm 6ft 1 and I weigh 9 stone 2 (BMI of 16.8)

[pennyannie in reply to MrMacast]

So your TSH is pretty much spot on - ' on point ' being 1.20/1.50

and generally speaking most people's unique set point is between 3.50 - 4.50 T3 /T4 and if you divide your T4 result 24.40 by your T3 result 6.20 you will get around 3.90 putting your metabolism pretty much in at the centre of the above little T3/T4 ratio :

Most people likely tend to run with a T4 at around mid way through the range with a T3 tracking in % terms slightly behind the T4.

You have already had your pituitary gland investigated and that has come back all clear - and I'm sorry but I now feel out of my depth as to if this is a thyroid health issue :

[MrMacast in reply to pennyannie]

That’s what endocrinologists are telling me that it isn’t a thyroid issue. In fact the last endocrinologist told me my results came back “normal”.

So is just T4 on its own not as important as the T3/T4 ratio?

Could it just be the lab I’m using privately have strict ranges, and the ones used by my endocrinologists are coming back as in the normal range?

[pennyannie in reply to MrMacast]

No - there is no such thing as a ' strict range ' - and there is no point using a range from the internet - or somewhere else -

You need to use the ranges given by the laboratory who ran the TSH, T3 and T4 blood test.

The T4 needs to be seen in relation to the T3 -

and if not on any thyroid hormone replacement the TSH is deemed all important and if also in range, along with a T3 and T4 in range - I doubt the NHS will take this further.

The T3/T4 ratio was to try and put your mind at rest - sorry if I've caused the opposite.

[MrMacast in reply to pennyannie]

Thanks for your messages. They really have helped me. I don’t know a lot about thyroid, only what I’ve tried to learn online. I don’t realise there was a T3/T4 ratio. If my results don’t indicate a thyroid problem, that’s fine. I just worry they’ve missed something, as my blood tests are saying “high FT4”, but then they’re not doing anything about it.

Can other things cause FT4 to be raised, such as nutrient deficiencies, etc? I’m underweight and have gut dysbiosis, and my diet is okay (by that I mean it’s not awful, but there’s lots I could improve on). Would a multivitamin help, (without iodine!)

[pennyannie in reply to MrMacast]

Well we recommend keeping core strength vitamins and minerals at optimal levels -

so these are ferritin, folate, B12 and vitamin D and optimal levels will be a good 50% through the ranges - with some NHS ranges are too wide to even be sensible -

as a female I now aim to maintain my ferritin up at around 100 - folate around 20 - active B12 125 ( serum B12 500 ++ ) and vitamin D up at around 125.

Multi vitamins are not recommended as they usually do not contain ' A ' grade contents and it's best to supplement individually what you are low in.

You can read much more about all things thyroid by going into Thyroid uk -

which is the charity that supports this patient to patient forum - thyroiduk.org

[MrMacast in reply to pennyannie]

Thank you so much for the information and your messages. I really do appreciate them! I've actually seen videos on how to check thyroid by swallowing and it's the first time I've really looked at my neck to check for nodules or goiter. What do you think?

youtube.com/shorts/Mj8BkPs6...

[MrMacast in reply to MrMacast]

I’ve uploaded another video that shows it in better light. You can see my thyroid moving when I swallow but not sure if that’s because I’m underweight, or if it’s enlarged and it shouldn’t be seen?

youtu.be/kOvXCxLJS6w?si=BZL...(Not working as expected?)

[pennyannie in reply to pennyannie]

Within Thyroid UK - I gave you the link yesterday - you will find a section on Private Testing Companies and it details the London Private Ultrasound Clinic - so maybe arranging a private scan there - may help you.

If your breathing or swallowing sense an obstruction in the throat -

maybe ENT is the next step but presume both the endo's have already done a physical and ' felt around your neck ' for anything untoward.

I'm sorry but I'm not able to take this further as I'm out of my depth:

[MrMacast in reply to pennyannie]

Okay, thanks for all your help, I’m really grateful.