Progesterones role. If you simply look its easy to fine plentiful sources.

[Doreen]

There is nothing I dislike more than misinformation spread in chat or in the forums, but here are 2 really easy searches that turn up the importance of progesterone (for those in doubt).  Doesn't mean all doctors will prescribe it, but it is half of the natural female cycle. Do your own research, ask your medical provider, and make an informed choice.  Don't just take any persons 'word' on it (including my own)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2481303/
https://www.livestrong.com/article/319391-the-effects-of-progesterone-on-the-breasts/