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Thyroid UK
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T4 getting lower..Why?

Hi again. After posting before I went back to GP and asked for T3 to be tested. She agreed and here are the results..

T3 4.9 (3.3-6.1)

T4 6.5 (9.8-18.8)

Tsh 0.08 (0.4 - 4.0)

In March T4 was 8.1. I was taking 50 T4 and 40 T3 but GP stopped T4 on Monday as she feels I am over medicated. My body tells me otherwise..I am feeling terrible and still have a 5 week wait to see Endo after waiting 8 weeks already. Just wanted any thoughts or explanations as to why T4 is lowering. I am also being sent for the short synacthen test.

Appreciate any feedback

4 Replies


You would expect T4 to be lower when medicating T3. You need T3 (active hormone ) to be higher to feel well.

I would have expected your doctor to have reduced T3 dose and increased T4 to increase the storehouse which helps with the conversion to further T3. T4 has a life of about a week so you probably won't feel the reduction yet.

Adequate cortisol is required for good thyroid hormone synthesis. High//low levels can lower thyroid hormone production & inhibit T4 -T3 conversion and increase the conversion of T4 to reverse T3.

If you have elevated thyroid antibodies these can cause inflammation which can decrease the sensitivity of the thyroid receptors so thyroid hormone isn't up taken and used in a healthy way resulting in hypothyroid symptoms no matter what the dose.

My results are very similar to yours as my endo keeps me low because of other health conditions. I have managed to get thyroid hormones working really well through healthy living, optimal nutrients and lots of adrenal support. The better you get thyroid hormone working, the better they on -going work.

Are you dividing T3 doses to keep thyroid hormone more stable ? ? ..


Thanks for that..I am taking all my T3 in the morning. The GP didn't want to change T3 as it was the Endo who prescribed it...think she was too scared to!



Thyroid receptor resistance can also be cause by low Vit B12 when homocysteine gets too high. Are you optimal in all nutrients and iron ?

You could dose the same daily amount of T3 but just divide it up. Many members take it in two doses. My endo has me dividing mine into three daily doses. I don't know if this to be any more beneficial than two and is a pain to co-ordinate..


Hi..GP would not test for B12 or iron as she had done a full blood count in January....I got the results and I cant see any iron, ferritin or B12 on the sheet. I will try splitting dose and see of it makes a difference. Appreciate your reply

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