As I has some hypothyroid symptoms I used a self-test: with following results:
TSH 1,74,
FT 4 11.6
FT3 4.2.
Test centre showed this as abnormal and needing follow up with GP. As a result of this GP took a full blood test across the range (including Vit B, iron, serum C, rheumatoid factor and more) - all of which were in normal ranges. However, they ONLY tested TSH and not FT4 and FT3.
Any advice about the lower range FT4 and whether this could be giving me fatigue and joint pain? If so possible ways to treat?
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It's very likely that you'll need two abnormal tests before anything is done, this is to ensure that it's not a non-thyroid issue that is causing the abnormal results.
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). If there is enough hormone then there's no need for the pituitary to send the message to the thyroid so TSH remains low.
In Primary Hypothyroidism, which is where the thyroid fails, the TSH will be high.
However, with Central Hypothyroidism the signal isn't getting through for whatever reason so the message isn't getting through to the thyroid to produce hormone, hence low FT4. It could be due to a problem with the pituitary (Secondary Hypothyroidism) or the hypothalamus (Tertiary Hypothyroidism).
As Central Hypothyroidism isn't as common as Primary Hypothyroidism it's likely that your GP hasn't come across it before.
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, but as I said you may need two abnormal tests before anything is done.
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 ThyroidUK 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.
The TSH (thyroid stimulating hormone) is a pituitary hormone. It signals thyroid to produce so if everything is working as it should a normal TSH should mean a normal FT4 & FT3 (Free thyroxine & free triiodothyronine) these are the actual thyroid hormones.
The thyroid produces T4 (thyroxine) & a tiny quantity of T3 (triiodothyronine) most T3 is converted from T4 but they should usually be well balanced.
The most useful test is the free unbound (available to use) levels of T4 & T3 (FT4 & FT3).
FT4: 11.6 pmol/l (Range 12 - 22) -4.00%
FT3: 4.2 pmol/l (Range 3.1 - 6.8) 29.73%
Your FT4 is under range & FT3 is 29% of range which is quite low & certainly be causing hypothyroid symptoms.
Sometimes the body prioritises conversion of FT3 as this is the active hormone but you would expect to see a high TSH as the levels are low.
So if similar results persist your doctor will need to investigate if an issue with HPT (hypothalamic pituitary thyroid) axis. (Feed back loop)
You may also want to test for thyroid antibodies.
TPOab (Thyroid Peroxidase antibodies)
TGab (Thyroglobulin antibodies)
Autoimmune issues affecting the thyroid can cause thyroid fluctuations but the TSH responds slowly so if levels are altering quickly the TSH might be rising / catching up.
Do you remember what time the blood draw was taken?
When you arrange blood draw it’s recommended to arrange first thing ideal before 09.00. No food or drink except water. Avoid any supplements containing biotin. It can affect the test & skew results.
Purple Nails, thanks very much for the detailed advice. I think I need to take another test through a test company to confirm the FT 4. Seeing GP is very difficult currently, and as they only test TSH, this leaves me in tricky place if the low FT 4 is confirmed. I have wondered if I can self-medicate if this is the case, since GP route seems such a challenge. I have been taking Vit D, magnesium, flax oil, and Gluscosamine, and vit C because of achy joints. My memory decline and fatigue has increased over the last ten years along with joint pain.
I think I need to take another test through a test company to confirm the FT 4. Seeing GP is very difficult currently, and as they only test TSH, this leaves me in tricky place if the low FT 4 is confirmed.
If you get another test with a low/below range FT4, I would show both sets of results to your GP along with the evidence linked to about Central Hypothyroidism, say this should be considered and will your GP either get FT4 tested himself or refer you to an endocrinologist.
thanks - have booked a second test, and will take it from there, has been very reassuring to have this advice as otherwise difficult to know how to move forward.
Reference ranges vary from lab to lab so when posting results we need the range that comes with it. Can you add them please, and the results/ranges for any other tests you had done.
With B12 and Vit D (if done) can you also add the unit of measurement please.
Serum vitamin B12 level 298 ng/L [211.0 - 911.0] - ng/L is the same as pg/ml.
This is low.
According to an extract from the book, "Could it be B12?" by Sally M. Pacholok:
"We believe that the 'normal' serum B12 threshold needs to be raised from 200 pg/ml to at least 450 pg/ml because deficiencies begin to appear in the cerebrospinal fluid below 550".
"For brain and nervous system health and prevention of disease in older adults, serum B12 levels should be maintained near or above 1000 pg/ml."
Do you have any signs of B12 deficiency – check here:
If you do then list them to discuss with your GP and ask for testing for B12 deficiency and Pernicious Anaemia. Do not take any B12 supplements or folic acid/folate/B Complex supplements before further testing of B12 as this will mask signs of B12 deficiency and skew results and if you have B12 deficiency is not detected and treated then this could affect your nervous system. B12 deficiency should be treated before starting folic acid because folic acid can sometimes improve your symptoms so much that is masks B12 deficiency.
If you do not have any symptoms then come back and suggestions can be made to improve your level.
Serum ferritin level 32 ug/L [10.0 - 291.0]
This is very low. Ferritin is recommended to be half way through range although some experts say the optimal level for thyroid function is 90-110ug/L.
As iron deficiency is, according to NICE, suggested when ferritin level is <30 I think it would be wise to ask your GP to do an iron panel. This will show if you have iron deficiency.
You should also ask for a full blood count, this will show if you have anaemia.
You can have iron deficiency with or without anaemia.
You can have low ferritin but not iron deficiency.
If you have iron deficiency or anaemia then your GP should address this. If not your GP may or may not prescribe iron tablets for the low ferritin.
You can help raise your level by eating liver regularly, maximum 200g per week due to it's high Vit A content, also liver pate, black pudding, and including lots of iron rich foods in your diet
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