Newbie trying to understand thyroid results

Hi everyone - My partner just got diagnosed as hypothyroid (still waiting to hear if it is Hashimoto's or just hypo). We're struggling to understand his test results though: TSH 25 (ref range 0.3-4.2) and T4 10.5 (ref range 12-22). It seems the T4 is just a little bit low but the TSH is massively raised! Does anyone understand why a little drop in T4 could be causing a huge rise in TSH? Does it mean the problem is likely to be happening in the T4 to T3 conversion? If so then taking thyroxine (as the doctor has now prescribed) probably won't solve the problem?

Thanks so much for any insights!

22 Replies

When the thyroid gland is struggling, the TSH rises and the T4 lowers. For the TSH to rise it doesn't happen overnight, could be happening for years before being diagnosed. We might not realise we are developing clinical symptoms initially or doctors may not have done a blood test for thyroid hormone. Other doctors only pay attention to the TSH and in the UK it has to rise to 10 before getting medication, whilst other countries prescribe for a TSH around 3+. If there is antibodies too, the diagnosis is Autoimmune Thyroid Disease, also called Hashimotos and it is the antibodies that attack the thyroid gland until the person is hypothyroid.

Thank you so much. What we don't understand is why the TSH is so very high (25!) when the T4 is only a little bit low? Is that because TSH is triggered by low T3 and not low T4?

My TSH was 100 when finally diagnosed. The Thyroid Stimulating Hormone (TSH) is from the Pituitary Gland not the Thyroid Gland.

The Thyroid Gland cannot produce the amount of thyroxine (T4) required to produce liothyronine (T3) which is the Active hormone required in all of our billions of receptor cells which enable us to function normally, i.e. the brain contains the most cells.

Thank you so much. Very useful paper by Dr John C. Lowe!

Hello athene,

Welcome to our forum and sorry to hear about your partners ill health.

The results are classic of undiagnosed hypothyroidism.

TSH (Thyroid-Stimulating Hormone) is released by the pituitary gland in response to low thyroid function.

T4 (Thyroxine) T4 is the inactive thyroid hormone, generally kept in storage in the thyroid gland until it’s turned into T3, the active thyroid hormone.

Treatment (thyroxine) is the same irrespective of whether thyroid antibodies are found or not and takes 7/8 days to be absorbed before it starts working and up to 6 weeks to initially saturate the body which will only tolerate small increases at any one time.

Your doctor should retest your thyroid hormone levels after 6 weeks and adjust the dose according to results. Leave 24 hours between last dose and blood draw and try to have the blood draw early in the morning when TSH is highest.

It is important to take your pill on an empty stomach with a glass of water, 1 hour before food, 2 hours before supplements and 4 hours before calcium, iron or vit D supplements.

The goal of Levothyroxine is to restore the patient to euthyroid status and for most people that means TSH just above or below 1.0. Beware that symptoms can lag behind good biochemistry by 6-8 weeks.

People with thyroid issues often have vitamin deficiencies and it is recommended that you have B12, vit D, folate and ferritin levels tested as optimum levels are required to ensure thyroid meds are absorbed.

I hope your partner feels better soon,


Getting Diagnosed


This following link explains the importance of vitamins and where they may be obtained. This forum is supported by the charity ThyroidUK. You do not have to join the charity to benefit from this forum but by doing so you will be supporting the charity and also entitled to various discounts when buying supplements, as detailed in the link below.


Disclaimer: I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


Thank you very much Flower 007. We are slowly starting to understand more about the condition. It is very confusing as my partner does not really have many symptoms, maybe a little bit more tired than usual but nothing dramatic. He'll probably get a second test done just to confirm the results (according to one of the articles recommended by Shaws above, TSH, T4 etc can vary quite a lot hour by hour) and also to get the T3 and rT3 tested, and then decide what to do. It's hard to take medication when you don't feel unwell, just on the basis of a number in blood test. And I guess he also worries that if the problem is more one of converting T4 to T3 then just taking thyroxine won't help. Apparently it can just build up in the blood and then you end up with hyper as well as hypo symptoms!

My heart goes out to everyone out there with this difficult condition!


A repeat test is often required when the patient has boarder line hypothyroidism as the TSH is variable.

However with a TSH of 25 it would be considered for hormone replacement to be necessary.

Free T3 (and RT3) will give a clearer picture. It is also wise to get thyroid antibodies tested TPOAb & TGAb.

The T3 result will be interesting seeing as there is a high TSH with no usually symptoms. Many patients would feel quite unwell with this level of TSH.

Post results complete with ranges (numbers in brackets) for members to comment.



Disclaimer: I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


Thank you Flower. I will post the antibody and other results when we get them. It's encouraging to know TSH is variable. Hoping for better numbers next time...

I also meant to say B12, folate and ferritin were all in range though possibly not optimal. We take vit D but rather erratically. Definitely scope for improvement there!

Some hints for when future blood tests due:-

Make the earliest appointment and fast (you can drink water).

Leave about 24 hours between the last dose of levothyroxine and the test and take it afterwards.

Vitamins and supplements I take at lunchtime so as not to interfere with levothyroxine. Iron has to be 4 hours apart from levo.

Get Vitamin B12, Vit D, iron, ferritin and folate tested too.

Always get a print-out of the results with the ranges for your own records and if you have a query you can post for comments.

Thank you!

You made a reference to getting Free T3 and reverse T3 measured above. Be aware that you will be very lucky indeed to get Free T3 measured by the NHS. You won't get reverse T3 measured at all.

For a full set of thyroid function tests your only choice is to do a test privately.

If you look on this page :

you will see some blue "badges" referring to "Thyroid plus ten" and "thyroid plus twelve" testing.

I would have thought the +10 test would be fine, but it is your choice.

If you want vitamin D tested (the +10 doesn't include it), then it can be done fairly cheaply here :

All the tests I've linked to require finger-prick samples of blood, rather than blood being drawn from the arm with a needle.

Thank you. It's great you can do thyroid tests with just a finger prick! I think it's worth paying for T3 and rT3 to try and understand the full picture before putting oneself on a lifetime of medication.

Athene, your partner is extremely fortunate to be asymptomatic with TSH 25 and FT4 below range. Nevertheless he needs thyroid replacement otherwise FT4 will continue to drop and TSH will rise and he will become symptomatic and will suffer health complications.

The starting dose of Levothyroxine is usually increased by 25mcg every 6-8 weeks until the patient is euthyroid which for most people will be when TSH is 1.0 with FT4 in the upper range and FT3 towards or in the top third of range.

TSH is a pituitary hormone and rises when low FT4 and FT3 are detected, and drops when sufficient hormone is detected. FT4 measures the free T4 available for conversion to T3. When FT4 is low FT3 will usually be low because there is insufficient T4 to convert to T3. A proportion of T4 converts to T3 which is the active hormone, and a lower proportion converts to rT3 which is inactive. rT3 is the body's brake on overproducing T3. High rT3 occurs when Levothyroxine is unconverted. Because your partner has just started replacing low T4 with Levothyroxine it is highly unlikely he will have high rT3.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.

Thank you very much, Clutter. That puts it beautifully clearly!

Thank you for this great group - so glad I found you!

Actually, the FT4 isn't 'just a little bit low'. I would say it's massively. Because it doesn't just need to be 'in range', it needs to be up near the top of the range to have enough to convert to T3. I dread to think what his FT3 looks like!

Thank you. We will have it tested and I'll report back. The odd thing is he doesn't have a lot of symptoms and feels fine.

That's often the case. Not odd at all. I didn't have much in the way of symptoms, either, at the time I was diagnosed. Just a weight problem. Although, all through my life since early childhood I'd been having what I now know to be hypo symptoms, but they were all just dismissed by doctors who knew about as much about thyroid as I did at seven years old!

But, do you know, there are over 300 symptoms of low thyroid. He doesn't have to be depressed, losing his hair or putting on weight, to qualify. Could be he does have some and doesn't realise they're connected. Is he perfectly fit and healthy? Would be a miracle if he were. Most people have some niggles that they just ignore. Well, those niggles could be due to his low thyroid. Does he have an ingrowing toe nail, or dry skin? Bags Under his eyes? Broken veins in his cheeks? A spotty bum??? :) Or a cold one. All these are symptoms of low thyroid. They could all, individually, be due to 'something else', but when you have a whole bunch of them, that's when you should suspect thyroid.

How interesting Greygoose! You read so much about people who have nasty thyroid symptoms even when their bloods are OK and treatment seems to be working. And then there are people with no symptoms and rotten blood numbers. I have to admit my partner does have a few bags under eyes and bottom spots! I would never have have thought thyroid - quite incredible!

Well, we're all different. And how your bodies work is highly individual. Nothing surprises me anymore. :)

A quick update: we just got more test results and it turns out to be autoimmune hypothyroidism. Full results:

TSH 23.47 mIU/L (0.27 - 4.2)

FT4 10.5 pmol/l (12.0 - 22.0)

TOTAL THYROXINE(T4) 77 nmol/L (59 - 154)

FREE T3 4.2 pmol/L (3.1 - 6.8)

Thyroglobulin Antibody 560.5 IU/mL (0-115(Negative))

Thyroid Peroxidase Antibodies 108.4 IU/mL (0 - 34)

Seems strange that Total T4 and FT3 are both low-normal while TSH is so high and T4 low. But I guess it may explain why he hasn't felt worse.

From what I have read it may be an idea to have an ultrasound to try and establish the extent of damage done to the thyroid, and thus the chances of ever managing to come off thyroxine (with an AI diet, stress management etc). He hasn't started thyroxine yet, but will do soon, after seeing the endocrinologist.

Any thoughts, comments or advice would be very welcome. Thanks everyone for all your support!

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