Estrogen has a number of different roles within the human body. The function of estrogen is perhaps most closely associated with the development and operation of the female reproductive tract. In addition, however, estrogen plays a critical role in bone health and in the production of certain proteins important for proper body function. Estrogen can sometimes have a pathologic effect on the body because it can promote the proliferation of certain female cancers.
Most people associate the function of estrogen with its actions on the female reproductive system. Indeed, estrogen plays a critical role both in the development of the female reproductive organs and in the ability to carry a successful pregnancy. One of the first roles that estrogen plays in a woman's life is during puberty. During this time period, elevated levels of estrogen promote the development of sexual characteristics in women. It allows for the growth and development of breast tissue, redistributes body fat into an adult female pattern, and promotes the maturation of the internal reproductive organs including the uterus and fallopian tubes.
Another function of estrogen is to facilitate conception. During the menstrual cycle, it promotes the growth and development of the uterine wall in preparation for the possible implantation of a fertilized egg. A surge in its levels halfway through the menstrual cycle promotes ovulation. Estrogen also plays an important role in allowing fertilization of the egg, as it helps the cervix produce a thin, watery mucus that facilitates sperm transport to the mature egg.
Although many people think that the only function of estrogen is to assist the female reproductive tract, estrogen actually has many other purposes in different parts of the body. It plays an important role in the metabolism of the bone, as it decreases the turnover of bone cells, and thus promotes having a strong bone mineral density. This role becomes obvious after women enter menopause and have decreased levels of estrogen in their bodies because their bone mineral density decreases, putting them at risk for developing osteoporosis. In fact, certain medications used to treat osteoporosis have estrogen-like effects in the body in order to increase the bone density.
Promoting the production of certain proteins in the body is another function of estrogen. This role of estrogen is important in men and women alike, as men do have low levels of estrogen circulating in their blood. Estrogen increases the production of certain proteins important in causing the blood to clot. It also ramps up the creation of proteins that carry other hormones.
In some cases, estrogen can have a pathologic role in the body. Cancers found in women, such as uterine cancer or breast cancer, can have estrogen receptors on the malignant cells that comprise the tumor. The estrogen thus promotes the growth and spread of these cancers. As a result, some cancer treatments involve using chemical species that antagonize the actions of estrogen in the body. These medications are particularly important in fighting breast cancer.