I'm intregued by the idea that cycling might help breast development? Is it theoretical or observational?
The times when a biological female's breasts grow most are when she is NOT cycling. Though of course co-incidence doesn't equal causation, so i'm not saying cycling stops normal breast growth, just it doesn't co-incide with it.
Naturally breast tissue grows most before the start of menstruation (about 9 to 14 years of age) then growing trails off during the first few years of mestruation (~12 to 16 years, and the first few years of menstruation are usually not a regular cycle, more erratic). Then the hormonal cycle becomes regular as breast growth slows (15 to 18 years).
While a woman is cycling, only the fatty tissue of breasts can grow, and it only grows proportional to over-all weight gain, no faster than belly or thighs. Then, if a woman gets pregnant her breats begin to grow again and her cycle also stops.
The only other time an adult woman would grow extra non-fatty breast tissue is if she is on certain hormonal contraceptives so, again, not typical cycling.
Womens breasts do fluctuate in size durring the menstrual cycle, but they alwayse return to their normal size again. I think it's more of a swelling than a growing. Maybe they get more fluid in them rather than actual cell growth.
So, to the best of my knowledge, cycling hormonal levels are associated with breast growth stopping. Are you sure you are getting a real increase not just a fluctuation?
However a fertile woman's breast tissue is maintained, whereas at menapause (when cycling stops) breast tissue deteriorates a bit i think? Maybe cycling your hormones would help with breast tissue maintence. But i think a menapausal woman's overall eostrogen and progesterone levels drop, hence huge market in HRT.
But generally, a sustained surge of female hormones (like in puperty and pregnancy) would lead to more breast growth than cycling?
Also, you should make sure to take good care of your breasts. It is possible (but rare) for men to get breast cancer, but that's only lack of tissue volume to get sick. So, if you have the ammount of tissue matches a bio-woman, i assume the risk would. The risk may even be greater for a transwoman, because breast-feeding is one of the best things to lower breast-cancer risk, and few (if any) transwomen would get the opportunity to do that. So you should make sure you self-examine and/or just have good "breast awareness" and notice anything that looks odd. Try to find some public health websites from your government on breast awareness, one of the responsibilities of taking good care of yourself as a woman. Take good care of your new wommanly attributes, gals.
Sorry if i'm ranting, i'm just rather facinated by biology.