Thyroid UK

Why thyroid patients on thyroxine might find it harder to lose weight

Was doing a bit of reading on glucagon and came across some info that high levels of glucagon cause T3 levels to drop and RT3 levels to rise. And it does this by affecting the liver and preventing the conversion of T4 to the active hormone T3 (not by affecting secretion by the thyroid).

So I would imagine this would mean that if you don't have a functioning thyroid and you are on T4 (therefore rely fully on liver conversion for T3) dieting would cause low blood sugar which would cause high glucagon which would in turn cause hypothyroidism by reducing T3 levels. Thereby causing the metabolism to slow and less calories to be burned and no weight loss. Also causing other hypothyroid symptoms too I would imagine.

One argument for giving thyroid patients T3 as well as T4.

2 Replies

I have had a TT and weight is a constant battle for me. Now I am taking T3 as well, I have lost a stone since December (slow and steady!) so I second all you say, but it's good to see a reason. Thanks for this post.

Marie XX


So would this be the reason I manage slowly to lose weight and then my thyroid goes out and I end up heavier? Just been put on 20mcg of t3, would you recommend I try again? Fed up with the swinging back and forth. Dieted hard 4 times now with the same result. Seeing my gp tomorrow to demand a thyroid specialist, my guy is nice and willing to let me try t3 but readily admits he's not sure how it works. His speciality is diabetes.


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