Yes. Boobs consist primarily of fatty tissue and ductile tissue. Estrogen causes the fat cells in the boobs to enlarge. Testosterone has the opposite effect. Boob size usually decreases following menopause due to a decrease in estrogen level. Steroid use can masculinize a female body builder to the point where her boobs virtually disappear. In women with polycystic ovarian syndrome, the excessive testosterone secretion also may cause boob size to decrease. A lactating woman has larger boobs due to the engorgement of milk in the ductile tissue. Her boob size usually decreases after she has stopped breast feeding.
