Thyroid UK

Different TSH levels on different NDT with same t3 level?

Let's say two NDT tablets raise t3 to the same degree. Is it possible that one brand would put TSH to value 2,5 and another brand would lower TSH to 0,02 when keeping/raising t3 to the same value?

When I was on Erfa my TSH levels was 0.72 and T3 was 4.79. On thyroid-s my TSH was 0.01 and T3 was 4.53 (ref. range 2.6-5.7). I am trying to find out why. My guess is that with tyhroid-s I was getting more T3. But because I did lab test 12 hours after last intake the results wasn't reliable because of T3 release time. If I did lab test 4 hours after it would probably show t3 number above 6 which is enough to suppress TSH so much.

So what I am wondering is if erfa released more stable t3 and tyhroid-s more promt t3 or the reason is just about different t3 levels absorbed.

4 Replies


I would say it is unlikely.

TSH fluctuates throughout the day and is highest early in the morning. Blood tests taken in the morning and at night will have very different TSH values but FT3 values would also fluctuate.


I always take blood test at morning 12 hours after last dosage. I modified my question with some extra details.


If it was about the T3 itself, it would be the FT3 that varies, not the TSH.

As TSH varies throughout the day, I often wonder if it doesn't vary from day to day. But, then, so many things can affect it.


that's interesting..i am on nature throid and my tsh is low .04, my free t3 and free t4 is also low normal and I am taking 1.5 grains once a day...and dr says she cant increase bec of tsh going too low and it must be my lack of hormones suppressing t3 t4..mmmmmmm ..I am lost


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