Misconceptions:

In the past, popular and medical literature often erroneously referred to estrogen as a single hormone exclusive to women.  The term “estrogen” actually refers to a group of chemically similar hormones with the three most important being estrone, estradiol (most abundant) and estriol, which men also produce. However, the function estrogen performs in men isn’t entirely clear. Therefore, it’s important to not make generalizations about estrogens, because they are not all the same.

What are Hormones?

Hormones are necessary chemical substances in humans and animals. Hormones are referred to as “chemical messengers” that transport information and instructions from one group of cells to the other. In the human body these chemical substances manipulate all cells and organs. Hormones also play a part in other functions including those that regulate growth and development, tissue function, sexual function, how our bodies use and digest food, the reaction of our bodies to emergencies, and our moods and emotions.

What Does Estrogen Do?

The estrogenic hormones are uniquely responsible for female sexual characteristics in humans and animals. This hormone can basically be thought of as necessary to procreation and the survival of a fetus during pregnancy.

Estrogen starts to have an effect on a woman’s body during puberty. These changes include the growth and development of the vagina, uterus, and fallopian tubes, and the enlargement of the breasts through the growth of ducts, tissue, and fat.

Estrogens, in general, tend to promote cell division in hormone-sensitive tissue such as the breast and uterine lining. During the reproductive years of a woman’s life, the pituitary gland in the brain creates hormones that cause a new egg to be released from its follicle each month. When the follicle grows, it produces estrogen, allowing the lining of the uterus to thicken. After ovulation, progesterone production increases in the middle of a woman’s cycle to help nourish a possible fertilized egg, furthering its development into a fetus. If fertilization fails to occur, estrogen and progesterone levels drop significantly. If fertilization occurs, estrogen and progesterone work together to prevent ovulation during pregnancy.

Estrogen also contributes to the fatty content of female body contours, the maturation of the skeleton, growth of underarm and pubic hair, and pigmentation of the nipples and areolae. The hormone controls other metabolic processes, including bone growth and cholesterol levels.

Source: John R. Lee. M.D., and Virginia Hopkins, What Your Doctor May Not Tell You About Menopause: The Breakthrough Book On Natural Progesterone (1996), Time Warner Books, Inc, pgs. 34-40.