I was just asked the question whether it is OK to have Zero (or suppressed TSH) when on T4/T3 treatment (or any thyroid treatment).
This was my answer:
The research is clear.
A suppressed TSH when on thyroid treatment is NOT a concern at all, AS LONG AS 1) the person has no hyperthyroid symptoms and 2) FT3 is not above the range (but this has caveats).
The above statement is true on T4 and I will provide the research references below to back it up.
What about T4/T3 or T3-Only therapy?