Yes, it is dangerous to drive estrogen levels below normal with Arimidex. However, using a SERM such as Clomid or Nolvadex is beneficial, as it acts as an estrogen in just the places we want it to, but antagonizes estrogen where we want it to as well. There is some evidence they may even help protect us from prostate cancer. I use Clomid year 'round as part of my HRT.