What Is the Function of Estradiol?

Estradiol is the strongest type of estrogen and is found in both men and women. Often referred to as E2, estradiol maintains the health of the reproductive organs and facilitates the fertilization process in women. In both sexes, E2 plays a role in protecting the heart, bones, and brain. While estrogen levels drop dramatically for women after they undergo menopause, they rise slightly for men when they are older. Estradiol has, therefore, been linked to several diseases that tend to occur later in life.

As a sex hormone, E2 has several different functions in women’s fertility. First, it helps to build and protect the lining of the fallopian tubes, vagina, and uterus. This role is critical to get the embryo to attach to the uterine wall. Many women who experience fertility problems have low levels of estradiol. Second, E2 maintains the oocytes, or egg cells, in the ovary. Healthy oocytes lead to healthy embryos. Only the best oocyte is selected at each ovulation period to be released and possibly fertilized.

As a tissue builder, E2 seems to help protect women from heart disease by raising the levels of HDL, the “good” cholesterol in the body. When hormone levels drop in postmenopausal women, their risk of heart disease increases. E2 also helps protect bone density in both men and women by participating in a messaging system that suppresses an overly rapid growth of immune cells in the bone. If more immune cells are allowed to grow, they can block calcium absorption in the bone. This is why men with lower levels of this hormone in their system have been found to be more susceptible to hip fractures.

Cancer has also been linked to changing levels of E2 in both men and women. For men whose production of estradiol increases as they age, the hormone has been held at least partially responsible for higher risks of prostate cancer. In women, estradiol has been connected to breast and endometrial cancer, cancer of the uterine lining. Older men lose their protection from E2 as their hormone balance changes. The level of testosterone circulating in their systems is no longer sufficient to block excess levels of E2. Women who have stopped menstruating, and therefore shedding the endometriosis, have stopped shedding excess estradiol, too. Even though they are producing lower levels of the hormone over all, it can build up over time. Some men and women decide on hormone therapy to help reduce their risk of getting these diseases.