Does treatment for B12 deficiency reduce the need for thyroxine?

[Ordinary39]

Since being diagnosed with a B12 deficiency, my TSH has massively dropped and consequently my dose of levo has been reduced. My GP suggested going from 200mcg to 150 but was happy to settle for 175 as I was worried about reducing it too much. To be honest, 8 weeks on and I feel that I might need to reduce it even more as I feel over medicated.

Is this normal after commencing b12 injections? What other reasons might cause a reduction in the need for levo? I've been hypo for nearly 30 years and for the most part, the trend has been my requirement for levo has gone up over the years and I have previously been on 250mcg.

Thanks in advance

[C_S-]

I’m not sure. My doctor thought I was almost overdosing with B12 as there was so much in my system after I started taking a supplement. Then he read that thyroid sufferers don’t absorb it properly so need to have more in the hopes that some might be digested. So basically it will always show as a bit high as lots is just “floating about” and not being used properly. Plus that it’s not really possible to overdose on B12! But I seemed to be really really high so I cut out the supplements after all. But do you know, now that you mention it, I have been feeling a bit rough of late so this has jogged my memory and I’m going to start taking them again. So yes B12 is a necessity for us I’d say. And yours will be working faster with injections. So it could be lowering your need for so much levo as the thyroid gland is probably now more balanced. Seems logical to me. Good news fir you anyhow. I started to take less levo when I went on a combination with T3. That helped lower my blood pressure too. But that’s another story. I was told by my endo that I would need to be my own expert. Research and blogs like this have certainly helped me. Good luck.

[tattybogle]

I'm not sure about whether B12 injections might make levo dose become too much either.. it's an interesting question, but some other reasons could be; If your hypothyroidism is autoimmune in cause (Hashimoto's) which is a destructive attack on the thyroid.. then when it is attacked it dumps all the T4/3 it has in that part of the thyroid into the blood all at once. This causes a period of too much T4/3 which is unrelated to how much you took.. it eventually gets used up / excreted/recycled naturally ... but until this happens you will have symptoms of overmedication, and may need to reduce dose... once it's finished happening that bit of thyroid is effectively dead , so you then have less functioning thyroid than before.. and may need to increase dose again to compensate.

I've never found any information on how long this might take , don't know if were talking days /weeks, or months.

Also i found that after the menopause my dose of 150 became too much and now take 112.5mcg. ( estrogen has an effect on thyroid hormone binding/transport.. if you add HRT you sometimes need to increase dose of Levo, so maybe if we have less estrogen post menopause, we need less Levo ? ) My FT4 just kept going up on it's own, to 2x the normal range and even when i reduced dose from 125 to 112.5 .. it still went up more . so I tried reducing to 100, but become constipated and slow/cold.. so put it back up to 112.5 ..and a few months later the fT4 went down again.. (although it is still over range) I don't have an explanation , but in my case it definitely wasn't B12 injections. , but i do have autoimmune hypothyroid.

[shaws Administrator]

Your doctor should treat your hypothyroidism as normal

I have Pernicous Anaemia for which I get a quarterly B12 injection. which was diagnosed many years before I became hypothyroid

It doesn't interfere with my TSH result and I take T3 alone.

Blood tests for hypothyroidism were introduced for levothyroxine alone.

Before that there were no blood tests and we were given NDTs, gradually raised until we felt well again with relief of symptoms.

[humanbean]

Having thyroid disease reduces absorption of lots of nutrients from food. This is important because for hypothyroid people , low nutrients will reduce conversion of the thyroid hormone T4 (a storage hormone, given in the form of Levo) to the active hormone T3.

Every cell in the human body needs T3 to work properly. The symptoms of hypothyroidism appear when levels of T3 are too low.

Doctors rely on TSH to tell them about the health of the thyroid. But TSH is actually a pituitary hormone, not a thyroid hormone, and is not a good indicator of how hypothyroid or hyperthyroid someone is.

Free T3 is a much better measure of "wellness" in thyroid disease. Note that people feel well at different levels of Free T3. Some might feel best when it is 60% of the way through the range, others might need it to be 70% or 80% of the way through the range or a little bit over the range. We all have to find our own sweet spot.

With respect to Free T4, the sweet spot for most people varies much more than it does for Free T3. Some people feel best with no Free T4 or very, very little (they take T3 only). And others might feel best with it 90% of the way through the range. Again, we have to find out own sweet spot.

The major nutrients affecting conversion from T4 to T3 are Vitamin B12, Folate, Vitamin D and Ferritin (iron stores), which is why they get mentioned so often on this forum.

Note that there are other nutrients that can affect conversion too, such as selenium and zinc, but they are not tested very often.

So if you have low vitamin B12 and then you raise your level it should improve conversion of T4 to T3. Since the level of T3 is what determines how well we feel then raising vitamin B12 might reduce your need for Levo.

You might find this thread of interest :

healthunlocked.com/thyroidu...