Thyroid UK
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TSH, T3 and T4

I'm new here, so all help and suggestions gratefully received.

I was diagnosed as having an overactive thyroid some years ago and had the radio active treatment thus making me under active. I was started on a dose of 25mgs of Levothyroxine which has gradually been increased over the years to 50, then 75 then 100, and now 125mgs daily.

I still get my bloods checked every quarter as I remain unconvinced that I am on the right level of medication.

Can you please explain in simple terms what TSH, T3 and T4 are? My recent blood test showed:

TSH 2.58 (0.27 - 4.2)

T4 16.3 (12.0 -22.0)

4 Replies

Welcome to the forum, McSquirty.

Thyroid Stimulating Hormone (TSH) is a pituitary hormone which responds to thyroid hormones T4 and T3. TSH will be high when T4 and T3 are low, and TSH will be low when sufficient T4 and T3 are circulating. T4 is a prohormone or storage hormone which converts to T3. It is low T3 which causes hypothyroid symptoms.

TSH 2.58 is a little high for comfort for a lot of thyroid patients and indicates your T4 level 16.3 may be a little low. The goal of Levothyroxine is to restore the patient to euthyroid status. For most patients that will be when TSH is 1.0 or lower with FT4 in the upper range. FT4 needs to be in the upper range in order that sufficient T3 is converted. Read Treatment Options in Email if you would like a copy of the Pulse article to show your GP.

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Just found my most recent blood test results which show:

TSH 1.31 (0.27 - 4.2)

T4 18.4 (12.0 -22.0)

with the comment 'no further action'



TSH 1.31 and T4 18.4 are euthyroid (normal) and indicate you are probably adequately dosed. If you are still symptomatic there is scope to increase dose. Read Treatment Options in Email if you would like a copy of the Pulse article to show your GP.

Hypothyroid patients are often low/deficient in ferritin, vitamin D, B12 and folate which can present symptoms similar to hypothyroid symptoms. It may be worth asking your GP to do blood tests if you still feel unwell.

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Fantastic, explains why I feel normal!

Can you explain why sometimes I suddenly suffer from low mood, don't want to go out etc?


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