Her TSH came back at 2.3. Her GP said it was normal. She was told to continue as she was. She still felt exhausted by 11am, still struggled to find the right word in conversation, still felt cold when everyone else was fine.
So what is the “right” TSH? The honest answer is: it depends, and the debate in the medical literature is genuine.
What TSH is (and isn’t)
TSH — thyroid-stimulating hormone — is the signal your brain sends to your thyroid. It’s a useful, sensitive marker, but it’s a proxy: it measures how hard your brain is asking, not whether the request is being met at the cell level. A normal TSH does not confirm adequate T4→T3 conversion or a quiet immune system.
What the guidelines say vs. what the research shows
Most guidelines set a reference range of roughly 0.4–4.0 mIU/L, and “normal” is whatever falls inside. But within that range, the research has explored whether a lower target matters for symptoms. Several studies suggest that many treated patients feel best with TSH in the lower half of the range — roughly 1.0–2.0 mIU/L — and that TSH at the high end of “normal” can still accompany symptoms (Perros et al., 2023).
The key thing TSH doesn’t tell you
Even a low, optimized TSH doesn’t address the antibody attack. If your TPO or TgAb antibodies are still elevated, the autoimmune process is active regardless of your TSH number. That’s the gap that clinically-dosed selenium addresses — the conversion and the attack, not just the hormone level.
The takeaway: pursue a TSH that makes you feel well (work with your doctor), and separately check antibodies. They’re different questions.
