I used do do push ups when i was 15 till about 17 and grew a solid chest of muscle... since i stopped my breasts are probably larger and less defined from less working out. Started Proscar at 22, Looking back, maybe i did get slightly larger boobs, but i never knew of all these f*****g "side effects" of finasteride, which i never seemed to get, like a sh*t load of people im sure. The bottom line is... if they did get bigger, its so marginal that im sure no one would know... but then again, its probably just from push ups back in the day.
Either way, i believe Gyno is Extremely rare...