Don't know if I ever posted this here, getting so I do repeats, anyway here goes!
Essential Hormones for Breast Development
Last Updated: May 04, 2011 | By Louise Tremblay
The breasts are hormonally regulated tissues that respond to a number of hormones circulating within the body. The developmental cycle of the breasts begins in puberty, and extends to changes during pregnancy. According to the Ohio State University Medical Center (OSUMC), the breasts do not fully mature until a woman has produced milk. During puberty, the breasts undergo periods of cell proliferation and division, which causes the breasts to enlarge and develop.
Estrogen is the hormone that helps control breast cell proliferation and division. According to OSUMC, breast development during puberty begins after the ovaries start to secrete estrogen. This accumulates fat within the connective tissue of the breasts, causing the breasts to enlarge.
Estrogen is also released during the first half of the menstrual cycle, which enlarges the breast glands. Once estrogen levels decrease following ovulation, the breast returns to its normal state.
Progesterone is a steroid hormone that works together with estrogen to regulate breast development. According to the University of Virginia Health System, progesterone levels are low during the first half of the menstrual cycle, but contribute to breast development during the second half of the cycle, once estrogen levels are lowered.
Progesterone contributes to development of the breast by signaling for the formation of milk glands. Estrogen first induces enlargement of tissues within the breast, and progesterone ensures these tissues develop proper functioning within the breast to aid in breast development.
As a girl approaches adolescence, the first outward signs of breast development begin to appear. When the ovaries start to secrete estrogen, fat in the connective tissue begins to accumulate causing the breasts to enlarge. The duct system also begins to grow. Usually the onset of these breast changes is also accompanied by the appearance of pubic hair and hair under the arms.
Once ovulation and menstruation begin, the maturing of the breasts begins with the formation of secretory glands at the end of the milk ducts. The breasts and duct system continue to grow and mature, with the development of many glands and lobules. The rate at which breasts grow varies greatly and is different for each young woman.
Female breast developmental stages
Stage 1 (Preadolescent) only the tip of the nipple is raised
Stage 2 Buds appear, breast and nipple raised, and the areola (dark area of skin that surrounds the nipple) enlarges
Stage 3 Breasts are slightly larger with glandular breast tissue present
Stage 4 The areola and nipple become raised and form a second mound above the rest of the breast
Stage 5 Mature adult breast; the breast becomes rounded and only the nipple is raised
Each month, women experience fluctuations in hormones that make up the normal menstrual cycle. Estrogen, which is produced by the ovaries in the first half of the menstrual cycle, stimulates the growth of milk ducts in the breasts. The increasing level of estrogen leads to ovulation halfway through the cycle, and then the hormone progesterone takes over in the second half of the cycle, stimulating the formation of the milk glands. These hormones are believed to be responsible for the cyclical changes such as the swelling, pain, and tenderness that many women experience in their breasts just before menstruation.
During menstruation, many women also experience changes in breast texture, with breasts feeling particularly lumpy. These are the glands in the breast enlarging to prepare for a possible pregnancy. If pregnancy does not occur, the breasts return to normal size. Once menstruation begins, the cycle begins again.
