Hi! I had exactly the same question some weeks ago and I posted it here too.
I feel like my oestrogen is decreasing after exercise, especially if I go to gym (not so much after lower intensity aerobic exercise). I've been wondering if the exercise impacts the way I metabolise oestrogen as I cannot find another reason for this. I'm on HRT and keeping dose stable.
I'll follow this thread with interest if someone will come along with more information on this, and if there is any research on the topic.