why does one's estrogen get so high while on stims?

That is what I'd like to know. I was in a meeting and that is when the nurse called with my instructions for tonight and then of course by the time I got out and called them back, the office was closed. Ugh!! They are lowering my Follistim again. I am sure it is due to elevated estrogen levels, since that is always the case when my meds get lowered. I just don't get why my levels go so high. Is there some other reason for that that is being missed here? I feel like I am on levels of drugs that one would be on for an IUI. This is really scaring me. I think Dr S will be in tomorrow morning, so I plan to bug him until he gives me real answers, I don't get this.