I am not medically trained, and I am not diagnosing, but what could be indicated here is Central Hypothyroidism. This is where the problem lies with the hypothalamus or the pituitary rather than a problem with the thyroid gland. With Central Hypothyroidism the TSH can be low, normal or slightly raised, and the FT4 will be low.
TSH is a pituitary hormone, the pituitary checks to see if there is enough thyroid hormone, if not it sends a message to the thyroid to produce some. That message is TSH (Thyroid Stimulating Hormone). In Primary Hypothyroidism the TSH will be high. If there is enough hormone then there's no need for the pituitary to send the message to the thyroid so TSH remains low.
However, with Central Hypothyroidism the signal isn't getting through for whatever reason. It could be due to a problem with the pituitary (Secondary Hypothyroidism) or the hypothalamus (Tertiary Hypothyroidism).
Your GP can look at BMJ Best Practice for information - here is something you can read without needing to be subscribed:
You could do some more research, print out anything that may help and show your GP.
As Central Hypothyroidism isn't as common as Primary Hypothyroidism it's likely that your GP hasn't come across it before. You may need to be referred to an endocrinologist. If so then please make absolutely sure that it is a thyroid specialist that you see. Most endos are diabetes specialists and know little about the thyroid gland (they like to think they do and very often end up making us much more unwell that we were before seeing them). You can email Dionne at
tukadmin@thyroiduk.org
for the list of thyroid friendly endos. Then ask on the forum for feedback on any that you can get to. Then if your GP refers you, make sure it is to one recommended here. It's no guarantee that they will understand Central Hypothyroidism but it's better than seeing a diabetes specialist. You could also ask on the forum if anyone has been successful in getting a diagnosis of Central Hypothyroidism, possibly in your area which you'll have to mention of course.
With such low Ft4 result, normally TSH (message from pituitary) would be high
Your TSH is low, suggests central hypothyroidism
GP should refer you to endocrinologist
Email Dionne at Thyroid UK for list of recommend thyroid specialist endocrinologists...NHS and Private
tukadmin@thyroiduk.org
For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also EXTREMELY important to test vitamin D, folate, ferritin and B12
Low vitamin levels are extremely common, especially if you have autoimmune thyroid disease (Hashimoto's) diagnosed by raised Thyroid antibodies
Explain to GP lots of family members have hypothyroidism, autoimmune thyroid disease often runs in families
Ask GP to test vitamin levels and thyroid antibodies
Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .
This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip)
Private tests are available as NHS currently rarely tests Ft3 or thyroid antibodies or all relevant vitamins
If TPO or TG thyroid antibodies are high this is usually due to Hashimoto’s (commonly known in UK as autoimmune thyroid disease).
About 90% of all primary hypothyroidism in Uk is due to Hashimoto’s. Low vitamin levels are particularly common with Hashimoto’s. Gluten intolerance is often a hidden issue to.
T4 is a storage and transport form of thyroid hormone produced by the thyroid, it is turned into T3 which is active. Some T3 is also directly produced by the thyroid .
One explanation for the T3 being Ok whilst the T4 is extremely low is that the system is clever . It tries to maintain a decent , stable level of T3 (the active hormone) and so if T4 is low it produces more T3 proportionately so you can still function.
So your fT4 and fT3 results do sort of make sense, (but i've not seen anyone with an fT4 that low, <3 means it's so little our machine can't measure it )
The confusing bit is that the TSH (Thyroid Stimulating Hormone) would be expected to be high in response to the very low ft4.
TSH is a signal from the pituitary gland (with some involvement of the hypothalamus) to the thyroid gland. When hypothalamus and pituitary sense that the level of thyroid hormones is low, more TSH is produced which will make the thyroid produce more T4 and some T3.
So you see your TSH would be expected to be high not low with an fT4 of <3 .
As for what might be the explanation i'll shut up now cos i'm out of my depth, except to say don't worry , there are many reasons for odd numbers, and this includes 'interference' which can be caused by many things and basically means your odd results could be totally wrong anyway , and would need repeating , using different chemicals at the lab.
just to add , i agree with the others .... Central ( secondary )hypothyroidism would explain it , as would Tertiary hypothyroidism ( where the hypothalamus doesn't release TRH thyroid releasing hormone to tell the pituitary what to do)
If for some reason the pituitary is not sending out TSH, the thyroid is not being told to make more t4 /t3. so it isn't doing it. This can happen when there is nothing wrong with the thyroid itself.
So further investigations would be needed to find out why the TSH is not responding as it should. I'd expect you to be referred to an endocrinologist. Central hypo is not a thing GP deals with other than to suspect it from odd results like yours.
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Help with test results please
Help with Thyroid test results
Help with results please
Re-posting - thyroid & vitamin test results
Test results, what do they mean?
