Thyroid UK
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Hyper and Hypo - and TSH

I am a little confused - I thought my thyroid has been underactive (I have been taking Levothyroxine for over 20 years), I don't have goitre, but someone told me I could have an over active thyroid - can some one explain the difference please, and can someone who takes thyroxine be either - under active or over active?

These were my last blood test results in Nov last year.

TSH level - 2.81 miu/L 0.20-6.00miu/L

Vit D 63 nmol/L 75-150 nmol/L

Vit B12 625 ng/L 180-910ng/l

Folate 8.3 ug/L 5.40-24.00ug/L

Ferratin 51 ug/L 10.00-291.00ug

Corrected Calcium level 2.28 mmol/L 2.15-2.60mmol

My TSH in Jan this year was 1.33

6 Replies

As a very rough guide, that misses out lots of bells and whistles :

In hypothyroidism (under active thyroid), TSH is usually high in range or over the range. Free T4 and Free T3 would tend to be low in range or under the range.

In hyperthyroidism (over active thyroid), TSH is usually low in range or under the range. Free T4 and Free T3 would tend to be high in range or over the range.

Someone with positive antibodies may find that thyroid function test results fluctuate, sometimes quite dramatically, during an antibody attack on the thyroid. During an antibody attack cells in the thyroid are destroyed by antibodies. The destroyed cells release their thyroid hormones into the body, thus changing the results of thyroid function tests. Someone who is hypothyroid will become a bit less hypo, and may even start showing symptoms of having an overactive thyroid. It's a temporary, unpleasant illusion though - the relentless destruction of the thyroid means the patient will eventually become hypothyroid permanently as the thyroid becomes less and less capable of producing thyroid hormone.

Under normal circumstances, a hypothyroid person cannot miraculously become hyperthyroid. They can be over-medicated though, and that will give symptoms similar to hyperthyroidism. To solve this problem the patient just needs to reduce medication, they do not need treatment for hyperthyroidism.

A person with hyperthyroidism would never tolerate levothyroxine. It would make all their hyper symptoms much worse.


I should add one other thing...

In a healthy population the average TSH is somewhere around 0.5 - 1.5.

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Thanks - my last one was 1.33 - which is in the healthy range, so I still can't work out why I still having the exhaustion, have had lots of bloods done, and nothing ever shows up.


I did say my explanation left out lots of bells and whistles...

It is possible to have an apparently normal TSH while also having low FT4 or low FT3. The TSH is not what determines how well you feel, it is mostly your level of FT3. TSH is produced by the pituitary, not the thyroid. And if your pituitary is not functioning normally then it may not be capable of producing as much TSH as it should. There are many things that can affect the pituitary, including something as simple as a bang on the head. TSH is not a reliable guide to how well people feel, and if the pituitary is damaged then TSH must not be used as a way to monitor thyroid medication.

The problem for patients is that the medical profession almost always assumes the pituitary is working perfectly.

Another factor... Having less than optimal levels of minerals and vitamins will affect the ability of the body to convert Free T4 into Free T3.

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Thanks for the explanation! I was confused and uncertain about which I was. From what you have said and the conversation my doctor had when I was younger, I was hyper but became hypo and am still hypo now as an adult.

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Thanks - hadn't thought of it like that - and not thought really about the pituitary. I am hoping to try and see a private Endo - saw one yesterday, and it was a waste of time :-( I have a separate post on that. The only positive was that he agreed ( after me asking him), to do Free T3 Free T4 and anti thyroid antibody blood tests..


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