My Friend Has Been On Thyroxine For Many Years.a Couple

My friend has been on thyroxine for many years.a couple of months ago her T 3 was low and the md put her on liothyronine since that time she is extremely tired and has no appetite.
Her T3 is ok now but she does not feel like doing anything.
She is 86 but in very good shape mentally and she lives by herself.
Several MD s do not know what is going on and I am worried about her.
I am a medical technologist by the way.
I hope you may have a suggestion.
Thank you