I was prescribed DIM by my naturopath and take it alongside HRT. It raises one type of estrogen and lowers another, and is taken to promote estrogen metabolism in general rather than addressing absolute levels. Obviously people react differently to different things though. I don't understand it enough to explain, it's really complicated but it is to do with your detox pathways and making sure your body keeps the estrogen it needs, and gets rid of that which it doesn't and does it safely. It isn't a supplement to take on its own though, or without supervision in my opinion.