

Take all the oral versus rectal route stuff with a grain of salt. The studies thus far have been mostly done on cis women and were measuring blood levels directly, not results. The way that progesterone interacts with stuff like breast development is not super well understood either, nor are the levels at which good development can be expected. I read a study fairly recently that suggested that there was not a large difference in satisfaction rates for patients taking it orally versus rectally, both reported positive side effects. Empirically it is hard to accurately measure things like this.
I have tanner stage 5 breasts, and developed them to that stage before taking progesterone. My friend who takes hers rectally, and has for a couple years now, has tanner stage 4 breasts. Its anecdotal but I think is a good example of progesterone being less well understood.


I think this calculator might be useful here.