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Thyroid UK
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I'm new - What do all these things mean?

I am about to have a blood test on Thursday to see whether my thyroid is functioning normally. I have been reading the posts on these pages and am getting increasingly frustrated by my lack of knowledge about the subject - particularly when it comes to test results. I mean, what is T3 and T4, FSH (or whatever it is - I haven't made a note of all these abbreviations!) etc, and what exactly do they signify? What are considered 'normal' ranges? The doctor I saw was a lovely chap - the old-style family doctor - and I am sure that he would take the time to explain the results to me, but there's no guarantee these days that the same doctor will be handling the results or be so patient with someone asking questions. Any brief lexicon on the initials and what they stand for will therefore be very helpful! Many thanks.

3 Replies

Welcome to our forum and don't worry about your lack of knowledge as it would appear most medical personnel have very little knowledge either.

I will advise you of the most important thing when you are having a blood test and that it has to be the very earliest appointment, fasting (you can drink water). If yours is later, alter your test date and time. Also allow a gap of 24 hours between your last dose of levo and the test and take afterwards. This helps keep the TSH at its highest and prevents a reduction in our prescriptions.

The thyroid gland and its hormones enable our metabolism to run smoothly, i.e. every single receptor cell in our body requires the hormone T3 to function optimally . Our brain/heart contain the most receptor cells.

When we have insufficient thyroid hormones circulating we get clinical symptoms:-


If we have hypothyroidism the doctor will prescribe levothyroxine which is a synthetic T4 hormone.

We are provided with a starting dose of 50mcg and have a blood test every six weeks with an increase of 25mcg until our symptoms are relieved and the TSH is 1 or lower. Not higher as many medical professionals believe. Some stop increasing dose when the TSH reaches somewhere within the range which is probably about 5. In the UK, they make us wait until the TSH is 10 before prescribing.

So, on this forum, we educate ourselves by asking questions and learning slowly.

Most doctors only take notice of the TSH - (Thyroid Stimulating Hormone) which begins to rise as our thyroid hormones are failing. It is from the Pituitary Gland. The aim then is levothyroxine to bring the TSH to around 1 or below. Most doctors think 'somewhere' in the range is fine but it doesn't improve our health. T4 - levothyroxine - converts to the Active thyroid Hormone, liothyronine (T4).

A healthy thyroid gland produces T4 and T3 - T4 is levothyroxine and T3 is liothyronine and also calcitonin.


When we were prescribed Natural Dessicated Thyroid hormones before levothyroxine and blood tests were introduced, we only got prescribed NDT.

Blood tests can include TSH, T4, T3, Free T4, Free T3 and thyroid antibodies but rarely are all of these tested and some members get their own blood tests.

We also have to have an optimum B12, Vit D, iron, ferritin and folate as deficiences also cause symptoms.

always get a print-out for your own records and you can post if you have a query.



A good place to start is here thyroiduk.org/tuk/testing/t...

Work through the purple menu on the left hand side.

Best time for thyroid tests is the earliest appointment of the morning and fast overnight although you can have water (have breakfast when you get home). This gives the highest possible TSH which is needed for diagnosis, an increase in dose of Levo or to avoid a reduction. TSH lowers throughout the day and after eating.

Any questions, just ask :)


Thank you so much for your replies - very helpful. I have at least 51 of the applicable symptoms (I'm over 60 so some definitely don't apply to me!), and it's all very confusing at the moment, although having read the list I think 'ah, so THAT's why such and such is happening!' At least, I hope it is, otherwise it's back to the drawing board....


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