Low T4, Low TSH but pituitary bloods normal

My GP did a large number of blood tests which the majority came back normal. I saw him yesterday and he said my T4 is low indicating hypothyroidism but my TSH is also low. The lab performed pituitary gland tests which all came back normal. I've been referred to an endocrinologist to see what's going wrong and where. Anyone else had the same? Never felt as run down but haven't been prescribed anything until specialist has seen me

5 Replies

  • Still sounds like central hypothyroid to me

  • This is an odd one. I deliberately don't advise on testing or diagnosis as a rule, but I think this case needs FT3 and FT4 doing, and a ratio of FT3/FT4 calculated, as well as looking at the actual values with respect to their reference ranges. Scenario 1): if your body tissues (not the thyroid) are trying desperately to convert what T4 there is to T3, then the ratio of FT3/FT4 will be high: usually the ratio is in the range of about 3-4/1 but in your case it might be up to 6 or higher. Scenario 2): The FT3 itself may be high enough in its range to suppress the TSH from the pituitary: thus the thyroid isn't being stimulated enough, and thus your FT4 will be lower. It looks to me in your case that this sort of explanation might be OK; namely your body has become an over- efficient scavenger of what T4 there is to make the maximum conversion to T3 (but though it lies within the ref range, not enough to make you feel well).

    Perhaps you could take this suggestion to your endocrinologist. Don't quote non-medical me though.

  • Sarahc1986 and Diogenes,

    This member has been diagnosed with tertiary hypothyroidism (hypothalmic) due to low FT4 and FT3 and good pituitary levels healthunlocked.com/thyroidu...

  • Yes, tertiary hypo could be the answer. In which case both FT4 and FT3 will be low and the ratio less different from the healthy one. But measurement of FT3 is essential to discover how well the body is responding to the trauma.

  • Hi Sarahc,

    You may be like me and be Tertiary hypothyroid. ( hypothalamus ) . When my bloods went hay wire both my FT4 and FT3 were way below range but my TSH never really got above 6.

    At this stage I was in a terrible mess mentally and physically.

    My endo had always assumed it was a pituitary problem but when pituitary bloods were tested and pituitary scanned nothing untoward was discovered. It was from this that my endo deduced that it was tertiary and not secondary.

    I would be really interested to know what your specialist has to say.

    Central is much rarer than primary hypothyroidism and can only really be controlled by measuring the FT3 level and being a little more lenient about FT3 ranges. I suspect the FT3 has to be very high in range to control symptoms.

    I've just had T3 added ( 15mcgs raising to 20 mcgs) to my 75 mcgs Levo so am still very early on in my journey. I also have painfully slow conversion.

    Don't feel well and relying heavily on TUK for tea and sympathy!

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