Slat I've tested this on myself, and I'd say there evidence for testosterone suppression with resulting loss of muscle. I've come off cold (ie. not PCT at all) and with something to jumpstart my T production again, and retained more LBM with the PCT.
FWIW I used freeze-dried garlic at 7000mg a day the last half of the cycle to keep my T production from suppressing, and stayed at that level for the first four weeks off.
I've read a FBB'ers who suggest actually taking stuff to increase E immediately aftercycle to avoid the sometimes substantial E rebound which can end up causing large muscle loss.
I like that garlic idea just haven't found the freeze dried stuff to try it. I think it would interesting to test it when not on cycle see what it does. I only get a bad esttrogen rebound when I take novladex it would be nice if there was something to help with that.