Estrogen belongs to a class of chemicals called steroid hormones--a family of hormones with a similar chemical structure to cholesterol. Estrogen is produced abundantly within the ovaries of women beginning at the onset of puberty and ending during menopause. Once produced in the ovaries, estrogen circulates in the bloodstream and signals to a number of tissues throughout the body. Estrogen in the blood leads to a number of biological effects in a range of tissues.
Breast Growth
A natural effect of estrogen on the body is in stimulating breast growth. Cells within the glandular tissue of the breast contain an estrogen receptor protein. Estrogen in the bloodstream binds to this receptor on the surface of the breast cells and initiates a signal to promote breast cell growth. During puberty, surges in estrogen levels promote prolonged breast cell growth and allow for normal breast development, according to the Ohio State University Medical Center. Estrogen continues to play a role in breast growth after puberty as well. Estrogen levels cycle during the menstrual cycle, and high levels of estrogen trigger breast cell growth in preparation for the possibility of pregnancy. Disrupting normal estrogen levels in the body can lead to menstrual irregularities and changes in normal breast growth.
Pregnancy
Estrogen also has an effect on pregnancy. In addition to helping prepare the body for pregnancy during menstruation, estrogen levels also help maintain pregnancy. Sustained estrogen levels are required to sustain pregnancy and play a role in fetal maturation during gestation. The University of Illinois notes that estrogen is produced in both the ovaries and uterus during pregnancy. This estrogen aids in the maturation of the uterine lining to allow successful implantation and promote the growth of blood vessels needed to nourish the growing embryo. Although the role of estrogen in supporting pregnancy is not get fully understood, the need for estrogen for successful pregnancy has been established.
Brain Function
Estrogen also plays a role in brain function, and many specialized nerve cells within the brain contain the estrogen receptor, responding to circulating levels of estrogen. A study published in the Journal of Neuroscience in 2006 explains that several nerve centers of the brain respond to estrogen and interact with hormone systems within the body. Estrogen is thought to improve cognitive ability and aids in memory. Estrogen also protects cells within the brain from degeneration that can occur during the aging process, normally causing slight memory loss and absentmindedness. Furthermore, estrogen is thought to play a role in preventing clinical depression. Although the research into the effects of estrogen on the brain is ongoing, the study indicates that the effects of estrogen on the brain may help explain cognitive changes that many women experience during menopause, when estrogen levels drop significantly.
