Can someone explain what's going on....because this is quite scary! I often wake up during the night with my heart pounding and last night i woke twice with rapid pulse. I'm not taking any thyroid meds (tsh 4+) as drs say i'm normal but i read somewhere that excess thyroxine can get dumped in the system and cause problems like this. I don't feel hypo, more hyper with widespread muscle pain . It may have nothing to do with thyroid but i thought i'de ask anyway........someone might have something similar.......in which case i really sympathise!!!!!!!!