I wish I had done more research before having my mirena inserted a few weeks ago. I have endometrial hyperplasia and had taken estradiol to control my heavy periods. My new doctor suggested the mirena after I visited him with a period that had been going for almost a month. Since then my period has returned after stopping for about a week. What's worse is the painful cramps that have come with it. They are terrible. I've never had cramps like these ever. There's no way I can forsee keeping this in for months just to get over the side effects. If the cramping and heavy periods aren't gone in a few weeks, I'm having it removed. I'd rather take the estradiol. Does anyone know how long this has been on the market?