[blomst]

Progesterone is probably important for making sure that estrogen receptors in the breast continue to work. I've been becoming more and more estrogen dominant since I started puberty (almost 5 years ago) but my breasts grew for less than a year, never rounded out, and the nipples did not reach a mature shape. My thighs and the bit below my belly button kept getting bigger though. Progesterone is crucial to proper functioning of estrogen, and the whole cycle in general - it must play a role in the development of secondary sex characteristics, even if it is not the thing directly causing growth.