Does NDT / levothyroxine raise blood sugar levels?

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I read on a lot of diabetes forums and see on drug inserts that if you take NDT, levothyroxine or cytomel that these can raise blood sugar / glucose levels. And if you are a diabetic taking these meds you should carefully monitor changes in blood glucose.

I find a little info about this, but not too much.

Has anyone had any experience with this or studies about about this?
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I Think it has to do with Cortisol levels. More T3 will increase Cortisol and that will result in insulin resistance. A diabetic that has taken prednisone can tell you what happens.


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I Think it has to do with Cortisol levels. More T3 will increase Cortisol and that will result in insulin resistance. A diabetic that has taken prednisone can tell you what happens.

So does an increase in T3 always cause an increase in cortisol?

I wondered about BG because my own small increase in BG coincided with my taking NDT thyroid. My BG had been floating about 100 anyway, so going to 109 wasn't exactly earthsharing, it had been there once before. But this time A1C also moved up to a new high of 5.8%, which was a new thing.

I don't think i really "need" ndt, it was only to move T3 up in range from 2.7 > 4.2. I was mostly hoping it would help with weight loss and it's hard to differentiate symptoms of feeling fatigued from over training, just starting out with TRT and getting older.


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I had also read that study, but hard for me to say it should increase insulin sensitivity when I read the details.

" Insulin sensitivity significantly improved only in subjects with OH (P < 0·05)."

OH is overt hypothyroidism, which if you read what level that is, T4 below 5 ug/ml, while my T4 was 6.4, so normal.

What many argue is that T4, FT3 should be in the "optimal" upper percentile of the normal range, TSH should be in the lower part of the normal range. This isn't hypothyroidism as defined by any endocrine group.

Which begs two questions:

1) Why is being in the upper part of the FT3 range considered optimal? Is there some sort of study to confirm this?

2) What happens to BG / Blood sugar if you don't have hypothyroidism (either overt or subclinical) but just want a higher level of FT3 that is in the upper part of the range?

I doubt we can find a any kind of study that indicates what happens when we take low normal thyroid levels and move them to high normal. If there is such a study, I have yet to find it.

However, there are studies that indicate having FT3 in the lower part of the range is healthier for people over 65, and TSH that is around 2.1 is better for long term survival.

The Association of Reduced Thyroid Function With Longevity

Clearly I don't adhere to a strict orthodoxy of endocrine hormone ranges, as my normal TT level is around 350-400 ng/dl, which most doctors would consider low normal, while I feel better, find it easier to lose weight, have more energy and blood tests confirm I do better at 600-900 ng/dl or high normal.

So on one hand, I do believe being in the lower part of the total testosterone range is bad for my health and I want to be in the upper part of that range, I can't say that being in the upper part of the range for every hormone there is is therefor a good thing also.

I have tried NDT 3/4 grain, it did move my FT3 from 2.8 > 4.3, TSH from 1.8 > 0.972. Which seems like a big move for such a small amount. I could certainly "feel" it when I took it, I can't say it gave me more energy or made me feel better, it felt sort of like a caffeine overload. I didn't feel nervous, just an odd feeling in my head.

When I first tried TRT, it made a huge and obvious positive change. When I tried NDT, I didn't see much either positive or negative. I took it for about 2 months, I don't know if that is long enough, I might try it again, I want to be on TRT for a longer time before I do it again.
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