Estrogen is the general name for a group of hormone compounds. It is the main sex hormone in women and is essential to the menstrual cycle. Although both men and women have this hormone, it is found in higher amounts in women, especially those capable of reproducing.
Secondary sex characteristics, which are the defining differences between men and women that don’t relate to the reproductive system, are determined in part by estrogen. In women, these characteristics include breasts, a widened pelvis, and increased amounts of body fat in the buttock, thigh, and hip region. This hormone also contributes to the fact that women have less facial hair and smoother skin than men.
It is also an essential part of a woman’s reproductive process. Estrogen regulates the menstrual cycle and prepares the uterus for pregnancy by enriching and thickening the endometrium. Two hormones, the luteinizing hormone (LH) and the follicle stimulating hormone (FSH), help to control how the body produces estrogen in women who ovulate.
Estrogen is manufactured mostly in the ovaries, by developing egg follicles. It is also produced by the corpus luteum in the ovaries, as well as by the placenta. The liver, breasts and adrenal glands may also contribute to its production, although in smaller quantities.
There are three distinct compounds that make up this hormone group: estrone, estradiol and estriol. During a woman’s reproductive life, which starts with the onset of menstruation and continues until menopause, the main type of estrogen produced is estradiol. Enzymatic actions produce estradiol from androgens. Testosterone contributes to the production of estradiol, while the estrone is made from andostenedione.
Estrogen is important to a woman’s health beyond just how it relates to her reproductive cycle. Although it can cause women to retain fluid, and early exposure through early menses can increase a woman's risk of developing breast cancer, this hormone has significant benefits. It can contribute to increasing high density lipoprotein (HDL), which is considered the “good” cholesterol, and lower the low density lipoprotein (LDL), which is the “bad” cholesterol.
After menopause, women experience a reduction in estrogen. This can lead to vaginal dryness, memory problems, hot flashes, fatigue, irritability and possibly one of the most devastating problems, a decrease in bone density. Although hormone replacement therapy has been controversial, with medical professionals debating its safety and effectiveness, menopausal women should consult with a healthcare professional for the safest and most effective way of dealing with changes in hormone levels.