TSH function questions

[th2304]

My current TSH level is very low, apart from being the triggering hormone to make thyroxine does TSH have any other function, and can low TSH have detrimental effect on anything else. Grateful for any info anyone has on this.

[Greybeard]

I've never seen any thoroughly reliable data that proves low tsh is dangerous. The reason I say this is because I've not seen anything that correlates tsh, t4 and t3. When talking about low tsh they may in fact be warning about the dangers of high t3, they don't measure it so who knows.

[th2304 in reply to Greybeard]

Thanks for reply. I have found it difficult to get any meaningful Thyroid function information from any NHS GP that I have spoken too. It just seems to be to follow NHS/NICE treatment protocol which is TSH and T4 blood test and prescribe Levo accordingly. NHS equals simplest and cheapest treatment. I wonder how many people have gone on to cost the NHS more in the long term because of developing other medical problems due to inadequate thyroid treatment.

[greygoose]

TSH - Thyroid Stimulating Hormone. Yes, it stimulates the thyroid to make T4 and T3. It also triggers - if that's the right word - conversion of T4 to T3. So, if you are taking T3 ready made, as it were, the production of TSH in the pituitary will reduce considerably, because you don't need it.

There is no proof that TSH does anything other than those two functions. Doctors believe that it's also somehow needed for hearts and bones, but they would be incapable of telling you in what way - ask one, just for a laugh! lol It's my believe that if TSH were necessary to avoid heart attacks and osteoporosis, it would be produced in larger quantities, anyway, and its production wouldn't be prompted by levels of thyroid hormone in the blood - which is the way it actually works.

And, quite apart from that, there has been research done that shows that the consequences of over-dosing on exogenous thyroid hormone, are not the same as the consequences - i.e. an increased risk (not a certitude) of heart problems and osteoporosis - of having high levels of T4 and T3 - and therefore low TSH - due to an over-active thyroid. So, doctors are scaring you needlessly.

[th2304 in reply to greygoose]

Thanks for reply, pretty much what I thought although I didn’t know it played a role in converting T4 to T3, having said that I don’t know what the conversion process is. From forum post it seems that inadequate conversion of T4 to T3 can lead to fatigue, low energy and brain fog all of which I have suffered from past few years. If TSH plays a role in conversion maybe too high T4 with too low TSH may impair T3 conversion ?, just a thought.

[greygoose in reply to th2304]

Yes, but it's more complicated than that. I really couldn't explain it all to you in detail, but the higher your FT4, the more is converted to rT3 and less to T3. So, having your FT4 too high is not a good idea, anyway. So many, many things can cause poor conversion, it's difficult to put your finger on the exact cause.

But, poor conversion will lead to low T3, which will cause all sorts of symptoms. It's the T3 that causes symptoms when too high or too low. The TSH doesn't make you feel anything, despite what some doctors think!

[th2304 in reply to greygoose]

Once I get back from holiday and get Medichecks blood test done, I may have more to go on, and armed with information from this forum may be able to get more accurate treatment. I had never heard of rT3 before so maybe that is a problem for me. Thank goodness for this forum, it’s clear that patients are better informed than most doctors.

[greygoose in reply to th2304]

If you have high rT3, that just tells you you have a problem. It doesn't tell you what it is. High rT3 can also be caused by many things, it's not just to do with conversion, and the test is expensive - they won't do it on the NHS! So, best really to illiminate the possible causes rather than do the test. For example, low ferritin, low-calorie diets, high/low cortisol.

For example, if your FT4 is high and your FT3 is low, your rT3 will be high. But, it's not the rT3 that causes the low T3. The most reasonable solution is just to reduce your dose of levo and add some T3 to it. And, you don't need an rT3 test to tell you that.

[th2304]

I can’t even get T3 done on NHS in our region let alone rT3 so will us Medichecks blood test to get a comprehensive test. Thanks for advice.