The Role of Estrogen in the Development and Health of A Woman’s Breasts
When estrogen acts on the receptors / target cells in a woman’s breasts, many changes can happen in the breasts.
In the immature breast, that is before puberty, the breast has cells that can be stimulated to grow and divide every cycle as a girl’s estrogen surges. However, the cells in immature breasts are not differentiated. That means that they are not able to produce milk. The immature breast also has what are called terminal end buds and tiny ducts. The following is an illustration of an immature breast.
During the reproductive years, that is when a woman is having a menstrual cycle, estrogen surges each month causing the terminal end buds to divide and multiply, the mass of the breast to increase, and for the breast to grow in size. Unfortunately, as a result of the monthly estrogen surges, more can go wrong with the breasts as they do not have enough time to repair the damage at the DNA (genetic) level that may eventually lead to breast cancer. The following illustration shows a maturing breast during the reproductive years.
A woman’s breast is considered to be mature once she has become pregnant. Pregnancy stimulates the terminal end buds in a woman’s breasts to produce milk glands. The more frequently a woman is pregnant and breast feeds, the more cell differentiation occurs in the breasts. Differentiated cells in a woman’s breasts are not as responsive to estrogen and don’t constantly divide therefore less can go wrong. This is believed to be one of the reasons why women who have been pregnant and have breast fed have a lower risk of getting breast cancer. The following is an illustration of a mature breast.
Researchers talk about the grandmother of a baby boomer having a 1 in 32 chance of developing breast cancer, the mother of baby boomer having a 1 in 16 chance of developing breast cancer, the baby boomer herself having a 1 in 8 chance of developing breast cancer, and her daughter having a 1 in 4 chance of developing breast cancer. One of the theories as to why a baby boomer today has a much higher risk of breast cancer than her grandmother is as follows.
Life expectancy of the grandmother of the baby boomer might have been approximately 50 years. During that time, due to a lack of birth control, the grandmother may have been pregnant several times, given birth to a baby several times, and breast–fed a baby several times. Considering the fact that a baby boomer’s grandmother might have had to up to 6 months between the birth of a baby and her starting another menstrual cycle, a baby boomer’s grandmother really did not have many menstrual cycles during her lifetime. Therefore, her breasts were not exposed to as many surges in estrogen during menstrual cycles. Also, the pregnancies and breast feeding of several children helped to differentiate the cells of her breast and protected her from breast cancer.
The report by the Women’s Health Initiative in 2002 shows conclusively that synthetic hormones such as synthetic estrogens and progestins can increase a woman’s risk for cancer. The following simplistic diagrams show how this might happen. The following illustration shows estrogen receptor sites, and a woman’s own estrogen [the red objects] floating in her bloodstream.
The following illustration shows how a woman’s estrogen [the red objects] attaches to the estrogen receptor sites.
Estrogen levels change in woman's body every 6 to 18 hours as an enzyme attaches to her estrogens and breaks them down. This is shown in the following illustration. The enzymes are shown as a green oval.
In order to be used by a woman’s body, synthetic estrogens are made so they can also attach to a woman’s estrogen receptor sites. This is shown in the following illustration. The synthetic estrogens are shown as a pink box attached to a red top.
The problem that occurs is that the enzymes cannot attach to synthetic estrogens and break them down in the same way that a woman's estrogens are broken down in her body. As a result, the levels of synthetic estrogens builds up in a woman's body, creating various side effects and increasing the risk of cancer. This is shown in the following illustration. The synthetic estrogens are shown as a pink box attached to a red top and the enzymes are shown as a green oval.