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Thyroid UK
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Latest Thyroid Function Test (Why Is TSH So Low ?)

Hi Everyone. I had a Thyroid Function Test this morning and I'm wondering why my TSH is so low despite FT4 not even being mid-range. My understanding, from this website, is that TSH should only be this low when FT4 is much higher, given that I'm on Levo only (no Liothyronine/T3).

>Latest Thyroid Function Test (Jun 2017):

Free T4: 14.4 pmol/L (11.00 - 22.60 pmol/L)

TSH: 0.06 mu/L (0.2 - 4.00 mu/L)

>Thyroid Function Test (Jan 2017):

Free T4: 14.9 pmol/L (11.00 - 22.60 pmol/L)

TSH: 0.02 mu/L (0.2 - 4.00 mu/L)

I was diagnosed in December 2016. Before Levo, TSH was 5.6, T4 10.8. I'm on 100mcg/day of Levo.

Any help, much appreciated.


2 Replies

In some people the pituarity simply shuts down production of TSH in response to levo and this situation goes unrecognised by TSH obsesed doctors

You have to treat on symptoms and ignore TSH in this situation its akin to having Central hypothyroid


Thanks reallyfedup123.


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