underactive thyroid
"After being hypothyroid for many years and having good results on Synthroid and natural thyroid, it went on backorder for a few months and I had to switch to Cytomel.  I felt immediate changes,  more alert and a little more energy.  However, after taking it for a few years,  about 70% of my hair fell out (in clumps and I tried everything to stop the hair loss), and I've had chronic insomnia,  huge appetite increase,  higher blood pressure,  anxiety attacks, hot flashes, etc. "