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 MECHANISM OF BREAST DEVELOPMENT |
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As a girl approaches adolescence, the ovaries start to secrete estrogen, inducing many changes in the body such as breast enlargement, appearance of pubic hair and hair under the arms. In the connective tissue of breast fat begins to accumulate and the duct system begins to grow. Once ovulation and menstruation begin, breast maturation continues with the formation of secretory glands at the end of the milk ducts. With months, many glands and lobules develop and the breasts reach their adult volume. The final volume of breasts and the rate at which they grow varies greatly and is different for each young woman. Estrogen,which is secreted by the ovaries in the first half of the menstrual cycle, stimulates the growth of milk ducts whereas the hormone progesterone secreted in the second half of the cycle stimulates the formation of the milk glands. During pregnancy, progesterone the growth of the milk duct system and the formation of many more lobules. By the fifth or sixth month of pregnancy, the breasts are fully capable of producing milk. As in puberty, estrogen controls the growth of the ducts and progesterone controls the growth of the glandular buds. Many other hormones, such as follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin, oxytocin, and human placental lactogen (HPL), aslo play vital roles in milk production. By the time a woman reaches menopause the levels of estrogen and progesterone begin to fluctuate, with levels of estrogen dramatically decreasing. With this reduction of circulating estrogen there is a reduction in the glandular tissue of the breasts, the connective tissue of the breast becomes dehydrated and inelastic. This leads to the "sagging" of the breasts often associated with women of this age. |
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| EFFECTS OF ESTROGENS ON BREAST VOLUME POSSIBLE MECHANISMS |
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 Breast Enhancement |
Estrogen effects on breast development are not yet completely understood. Many types of cells present in breasts are estrogen responsive. Estradiol acts on cells through binding to specific receptors ER  nd ER ß . Fat accumulation induced by estradiol can be explained by its binding to the receptors ER on adipocytes (fat cells) enhancing the number of 2a adrenalin receptors. These receptors block the lipolysis, allowing accumulation of fat. Then estrogen action results in adipose tissue development, enhancing the volume of breasts. Fortunately, this fat tissue increase is accompanied by an effect of estrogens on fibroblasts, the cells that synthesise collagen fibers which ensures the firmness of the breasts. Estrogens also stimulate the growth of wpithelial cells forming the milk ducts, thus developing the canal system and the rate of junction.Interestingly, estrogens stimulate the growth of nerve fibers that can decrete a factor called CGRP which has vasodilatory, increasing blood flow necessary for transport of the nutriments used for cell metabolism and milk formation during suckling.To summarize, estrogens stimulate the majority of the cells thus leading to a harmonious development of the breasts. |
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GRAPHS |
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 Breast Circumference |
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| Skin Elasticity |
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