I switched from Synthroid ,(after 25 years of feeling lousy on it ) to Armour, about 2 years ago.
With Synthorid.....at first, the dose was just too small for years(I was kept at a higher TSH).
Then, I switched to an endo who knew that optimal TSH was between 1 & 2. That guy tested my FREE T3....it was at the bottom of the range....he just ignored that. (I found all that out years later, after getting my old medical records). I went to him for several years.
I read the book "Stop the Thyroid Madness" & ""From Fatigued To Fantastic" and wanted to try Armour. I had to find a new doctor to do that. Immediately, I felt better!! But then the adrenal insufficiency caught up with me. (I had adrenal insufficiency because of the lousy treatment from Syntrhod all those years).
I took Cortef for almost a year. I took a tiny dose....that is mean to replace what your adrenals should give you . I had 5 mgs tablets & started out taking only one a day and slowly increased the dose to 4 tabs a day (spread out throught the day). Then after a while, I slowly, slowly decreased the dose and weaned off.
I feel so much better on Armour.
And why shouldn't I?
Armour is a blo-identical thyroid hormone and contains all the thyroid hormones that a human thyroid does (though NOT in the exact same ratio). Its been in use for over 100 years.
Synthroid is a SYNTHETIC version of ONLY ONE of the thyroid hormones . (Been used since the early 1970's).
Your body has to struggle to convert the synthetic T4 into the T3 you need. And if you're not doing that well enough, you won't feel your best (maybe not even close to it).