I am so glad I found this site. This is my second Mirena and I am having such problems!! I also have an under active thyroid and thought the way I have been feeling was something to do with that, but now I think it might be my coil. I loved the first one and had hardly any problems. My problems started when I needed a new one and got an infection, which made me tired and low, then I had my new Mirena fitted (& i have never felt such pain - had my first one fitted at the same time as having a laparoscopy - spelling??) and a lot of my troubles started. I have a lot of the symptoms others have listed and my main two at the moment are extreme tiredness and bad leg cramps and leg muscles aching. Have had loads of blood test for other stuff which are all showing nothing. My GP cant think of anything else and so is referring me back to the Endocrinologist. But the more I think about it (and read), the more I think it might be the Mirena causing a lot of my problems. I am in two minds whether to have it removed straight away though, because periods are also a living hell for me (only 1 good week in every 4), so I feel stuck between a rock and a hard place :-)