I was mid-diagnosed for 20 plus years. Always told I was borderline hypothyroid. Borderline always meant they wouldn't treat me.
Jump ahead 20 years and I finally got a diagnosis when my TSH was 7.23 and my free t3 and free t4 were bottomed out. I asked for a NDT but my Dr refused saying he wants to see how I do on T4 first. 6 months later I still felt awful, my free t4 was up and my free t3 never budged from when I was first diagnosed. Obviously I wasn't converting t4 to t3. At that point he put me on a combo of synthroid/ cytomel . Things got a little better but I was still feeling VERY hypo.
I asked to go on t3 only for a trial and he denied me so he got fired. I found out how to order t3 myself and have been self-treating ever since. My hypo symptoms are gone. My life , that I lost 20 plus years of, is back.
T3 is the only thing I will take for my thyroid. It works. Why wouldn't it? It is the active thyroid hormone our bodies need.