Cysts can definitely be caused by the Mirena. Progesterone affects smooth muscle which is the stomach, esophagous, intestines and other things. I had diarrhea once a month for 6 months while on ortho tri cyclin lo and the doctor said it was because of the change in progesterone from my other pill. He said the Mirena would be better beacuse of this, but I started feeling like my throat was closing and my appetite went away. I had the Mirena for 14 months before any symptoms showed and was diagnosed with IBS after having it taken out. I've written more about it in old posts. Sorry I don't have time to write more now, but I would definitely take it out. I think the cysts have something to do with your body trying to have a period, but never really getting there. And if they get too big, you have to have thiem surgically removed. I had a borderline one is size before having it taken out, but it must have shrunk because I haven't had any problems since.