I know it will seem complicated, however, we talk a lot about estrogen receptors, there are 4 estrogen and estrogen receptor signaling pathways. The red dots are E1-estrone, ER is estrogen receptors. When E1 binds to ER estrogen receptors it still has to make it to the nucleus of the cell and synthesize, that's where the cell divides (multiplies) and growth (breast growth) occurs. It's much more complicated than what I described, but hopefully you get the basic idea.






Estrogen synthesis and signaling pathways during ageing: from periphery to brain.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3595330/#!po=28.4091