Thyroid replacement preventing your own thyroid from working.

[raglansleeve]

I have read many times that by taking thyroid hormone replacement (T4), it actually prevents your own thyroid from working, and often makes things worse for that reason if your dose is too low. Is there any research I can use to explain this to my endocrinologist?

[shaws Administrator]

Your endocrinologist will know all about levothyroxine (also called T4) and they appear to have been instructed that they should prescribe levothyroxine initially.

The options we used to have have been removed by the British Thyroid Association.

There are thousands of people worldwide who do recover their health on T4. Those that do will not be looking on the internet for help/advice.

Mother Nature causes changes to our bodies and sometimes our thyroid gland fails us and we need thyroid hormones replacement for our bodies to work normally. T4 also called levothyroxine is an inactive hormone and should convert to the active hormone which is T3 - called liothyronine. We have millions of T3 receptor cells in our bodies and brain and heart contain the most.

For follow-up appointments always get the very earliest even if you have to make it weeks ahead. It is a fasting test (you can drink water) and don't take levothyroxine before but afterwards. Always take levo with one full glass of water and wait an hour before you eat.

Request B12, Vit D, iron, ferritin and folate at your next blood draw which should always be at the very earliest. TSH is highest then and drops throughout the day so that's why an early a.m. test is best.

Always get a print-out of your results for your own records and post if you have queries.

[raglansleeve in reply to shaws]

Thanks for the reply. I'm not sure that I posed my question correctly. On this board, I have often read that if you take thyroid hormone, it will replace the thyroid your own gland produces, rather than adding to it. For example, if you are hypo because your gland only provides 100 mcgs and you really need 150, if you start on a dose of 50, you'll actually feel worse because you're even further away from what you need since your body stops making the T4 completely. Still not sure if I'm explaining myself correctly here, and wish that I could remember which thread I saw this information on most recently.

[gabkad in reply to raglansleeve]

TRH > TSH > T3 = negative feedback loop. So if your T3 goes up because you are converting the T4 to T3, your hypothalamus and pituitary will apprehend this and lower their productions. That's why eventually people need a full replacement dose of thyroxine.

[Serendipitious]

raglansleeve,

It all depends. So if taking exogenous thyroid hormones pushes your TSH to a very low almost undetectable value this means the hypothalamus in the brain is not signalling the thyroid to produce it’s own supply. The body will stop using the sodium iodine symporter to transport iodine into the thyroid to make thyroid hormone. You might think that this doesn’t matter but it affects signalling in your brain which affects not just your thyroid HPT axis but also the HPA and HPO axis. In fact the hypothalamus is involved in so many other things.

The second image on this post explains this process.

instagram.com/p/CUHmh81oX2F...

[raglansleeve in reply to Serendipitious]

So if the exogenous hormone doesn't suppress the TSH to a significant degree, then one should still be also producing T4 and getting it from both sources? From what I've read here several times, it seemed that the science indicated otherwise. Good to know more now. Thank you.

[Serendipitious in reply to raglansleeve]

raglansleeve,

You also need the right nutrients to make thyroid hormone. One those includes iodine which can be controversial but it’s needed by that sodium iodine symporter. You need excellent digestion to break down your food and extract those nutrients. If digestion is poor then this will suffer. If you are stressed this will affect the the thyroid. There are lots of pieces to this puzzle.

[raglansleeve]

Thank you. My question had arisen because my endo is very reluctant to increase my dose, despite being only half of what is recommended for my weight, and I had been looking for "evidence" to support my request for a higher dose to address the symptoms that haven't fully resolved. I was deficient in both B12 and D (diagnosed about a year ago), but both of those issues have been dealt with via the supplement route. Our salt is iodized and folate is in all bread products here in Canada, and my iron levels are good too. I believe that I eat a very healthy diet too.

[Frodo in reply to raglansleeve]

Perhaps you needed B12 injections rather than supplements? Many people find supplements don't make a difference to symptoms although levels rise to 'normal' in the blood test.

[raglansleeve in reply to Frodo]

I hope that's not the case. My blood results were way over the top though, so hopefully the pill format was sufficient. Thanks for the suggestion though.