Why Do Breasts Grow?
When girls hit puberty, estrogen is released into the body and the breasts begin to grow. This tends to coincide with the beginning of menstruation. As the breasts grow, the milk ducts in them increase in size, causing the breasts to expand at the nipple. Then the breast tissue itself expands. According to TeenGrowth.com, breasts grow for about five to six years and generally stop growing by age 17 or 18. This is the natural end to breast growth. However, some things can affect breast size outside of puberty.
