Thyroid UK
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Low T4 and low TSH

I've had what I've been told is an underactive thyroid for many years and take Thiroyd thyroxine rather than levothyroxine. My T4 levels have always been low - 8,9,10 and with thyroxine they get up to 11 -12. T 3 tends to fall in range. TSH has been in normal range until this year but the last 2 tests show very low TSH - 0.02. Looking up on line it says this might indicate a thyroid disorder or have something to do with the pituitary. I also recently had 2 positive results to ANA screening (ENA anti-body screening & Anti RO 60 antibodies). Doctor was testing for Rhuematoid Arthritis as I have arthritis in one hand, but after an initial consultation with a Rheumatologist she said I have no RA symptoms and it's more likely something to do with the thyroid. The doctor didn't seemed concerned about the low TSH but I am concerned and think I should speak to them again. A couple of years ago I was tested for hasimotos which came back negative. Can anyone give any advice. Should I ask to be referred to an endocrinologist? Thank you! Louise

6 Replies


Blood tests were introduced for levothyroxine alone. Before that we were prescribed NDT which has T4, T3, T2, T1 and calcitonin or T3 added to T4.

Therefore if we take levothyroxine, T4 only the numbers cannot correlate when taking NDT or adding T3 or T3 alone. If T3 is in the product it will reduce the TSH.

It should be how we feel on a particular dose which is the best guide, i.e. relief of clinical symptoms. This is from a doctor who was an Adviser to TUK before his death.


Thank you!!


As far as I know, Thiroyd isn’t thyroxine, so you’re probably confusing folk there. :). It’s usually Natural Dessicated Thyroid - is that what you’re taking? Which is thyroid replacement hormone made from dried pig thyroid - many of us here take a form of that. It’s a mixture of T4 and T3.

How much Thiroyd are you taking? It’s not at all uncommon for TSH to be suppressed when you take NDT, so it doesn’t necessarily mean you’re taking too much. Do you have any recent FT3 results to share?


Hi there, I'm taking 90mcg, though recently feel very wired and can't sleep so just today decided to reduce to 60mcg. Yes Thiroyd is natural dessicated thyroid, and that's good to know TSH can be supressed on it, it's just that it's recently dropped from being within range to being very low. I will ask to have FT3 as I don't have that. Thank you for your suggestions, Louise


Thiroyd is NDT, not thyroxine and there are no test results for the most important test - free T3. The test interpretation was designed for those on levothyroxine only, so is not appropriate for people on NDT or T3. It is usual to have a low TSH and low free t4 when on NDT - the important results is Free t3 which you don't have. You also need ranges as each lab is different. TSH is not produced by the thyroid but by the pituitary gland and does not really reflect thyroid status when you are on medication. It doesn't cause symptoms itself or affect any other body system as far as medical science knows.


Ok thank you, so I need to ask the doctor to test free T3. I don't know whether it's better to try Levothyroxine for a while. Many thanks Louise


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