Liothyronine
"Adding 10mcg of Cytomel to my T4 medicine was just what my body needed to clear up those lingering hypothyroid symptoms that just wouldn't go away, no matter how good my lab numbers looked or other healthy habits I developed.  Doctors seem really hesitant to prescribe it, but if you're hypothyroid and T4 alone isn't working, your body just might need some T3."