Clenbuterol will increase thyroid output but only while your using it. Post cycle your natural conversion of T4 to T3 will be reduced hence why you could put weight back on if your thyroid slows down too much. Using Taurine 5-10g a day will help increase T4 to T3 conversion producing less of a rebound effect.
I mean everyday while your on clen! and possibly a few days after your off as well. This stuff will cramp you up hard from the taurine depletion it can ruin your workouts. You never know how you'll react though but its best to use Taurine with Clen in my experience, when i didn't use Taurine the weight would rebound back very quickly not to mention i couldn't handle any decent weight with the cramps in my forearms ouch! when i did use it didn't notice any rebound effect or cramping.
first of all, how long have you been using it? it could really help us help you more, if you have been using it for a while and suddenly stopped, check for hypothyroidsm, aka decreased T3 activity, such things as slow mentation, low BT, thinning hair. When the Anterior Petuitary's regulatory releasing hormones are inhibited because you are already supplying the hormone, it tends to stay inhibited therefore not making its own hormone anymore, you might experience all of the symptoms I mentioned in the beginning. I dont believe the thyroid should be messed with at all it targets all the hormones in the body and controls the ratio of oxygen to glucose inside your cells aka (Metabolic Rate) I cant help you anyfurther because I need more info.