hmm, I personally would wait a year (I ended up starting around the 8 month mark), but I would take that advice with a grain of salt given there are people who start prog from day 1 and have excellent breast growth - at the very least it’s not true that prog from day 1 will absolutely prevent normal or sufficient breast growth.

That said, it’s sorta hard to know what all is in play because people don’t always say what dose or route of administration they are taking. For example, taking prog orally does not sufficiently increase progesterone blood levels, and the liver basically absorbs >90% of the dose. So, would taking it rectally from day 1 cause the problems with breast growth people talk about, but taking it orally doesn’t due to the liver filtering it?

For those reasons, I would be cautious and wait a year, and then take it rectally. (Just knowing this is an area where there isn’t a lot of clarity, so that advice is liable to change as more evidence emerges.)

One reason to take prog, though, is that it does act as an anti-androgen, and that motivated me to start it a little early at the 8 month mark, to help me as I entered the final months before my orchi (which for insurance requirement reasons was only authorized after 12 months of supervised HRT).

Also, when doing monotherapy E injections, my E levels when high made it harder for me to sleep as long, so prog enabled me to sleep longer when I had those higher E doses.