I've tried it both ways, with and without. My E levels doubled, and are higher each time I see the doctor... meanwhile, the P that I was taking before seemed to balance my system. After P, I lost weight especially on my waist, but my breast shrunk also shrunk a bit (but now are back up to where they used to be). That's pretty much all that I've noticed.
I think I'm going to bug my doctor again for P, although, 'cause I figure it would be good to balance out my E since it seems to be crazy without the P, and I've been getting headaches, hot flashes, and a bunch of other not-so-fun things happening associated with my E levels being wonky.