Estrogen is probably the most widely known and discussed of all hormones. The term “estrogen” actually refers to any of a group of chemically similar hormones; estrogenic hormones are sometimes mistakenly referred to as exclusively female hormones when in fact both men and women produce them. However, the role estrogen plays in men not entirely clear.
In order to understand the role estrogens play in women, it is important to understand something about hormones in general. Hormones are vital chemical substances in humans and animals. Often referred to as “chemical messengers,” hormones carry information and instructions from one group of cells to another. In the human body, hormones influence almost every cell, organ and function. They regulate our growth, development, tissue function, sexual function, the way our bodies use food, the reaction of our bodies to emergencies, and even our moods.
The estrogenic hormones are uniquely responsible for the growth and development of female sexual characteristics and reproduction in both humans and animals. The term “estrogen” includes a group of chemically similar hormones: estrone, estradiol (the most abundant) and estriol. Overall, estrogen is produced in the ovaries, adrenal glands and fat tissues. More specifically, the estradiol and estrone forms are produced in the ovaries, while estriol is produced by the placenta during pregnancy.
In women, estrogen circulates in the bloodstream and binds to estrogen receptors on cells in targeted tissues, affecting not only the breast and uterus, but also the brain, bone, liver, heart and other tissues.
Estrogen controls growth of the uterine lining during the first part of the menstrual cycle, causes changes in the breasts during adolescence and pregnancy, and regulates various other metabolic processes, including bone growth and cholesterol levels.
During the reproductive years, the pituitary gland in the brain generates hormones that cause a new egg to be released from its follicle each month. As the follicle develops, it produces estrogen, which causes the lining of the uterus to thicken.
Progesterone production increases after ovulation in the middle of a woman’s cycle to prepare the lining to receive and nourish a fertilized egg so it can develop into a fetus. If fertilization does not occur, estrogen and progesterone levels drop sharply, the lining of the uterus breaks down and menstruation occurs.
If fertilization does occur, estrogen and progesterone work together to prevent additional ovulation during pregnancy. Birth control pills (oral contraceptives) take advantage of this effect by regulating hormone levels. They also result in the production of a very thin uterine lining, called the endometrium, which is unreceptive to a fertilized egg. Plus, they thicken the cervical mucus to prevent sperm from entering the cervix and fertilizing an egg.
Oral contraceptives containing estrogen may also relieve menstrual cramps and some perimenopausal symptoms, and regulate menstrual cycles in women with polycystic ovarian syndrome (PCOS). Furthermore, research indicates that birth control pills may reduce the risk of ovarian, uterine and colorectal cancer.
Other Roles of Estrogen
Estrogen produced by the ovaries helps prevent bone loss and works together with calcium and other hormones and minerals to build bones. Osteoporosis occurs when bones become too weak and brittle to support normal activities.
Your body constantly builds and remodels bone through a process called resorption and deposition. Up until around age 30, your body makes more new bone than it breaks down. But once estrogen levels start to decline, this process also slows.
Thus, after menopause your body breaks down more bone than it rebuilds. In the years immediately after menopause, women may lose as much as 20 percent of their bone mass. Although the rate of bone loss eventually levels out after menopause, keeping bone structures strong and healthy to prevent osteoporosis becomes more of a challenge.
Vagina and Urinary Tract
When estrogen levels are low, as in menopause, the vagina can become drier and the vaginal walls thinner, making sex painful.
Additionally, the lining of the urethra, the tube that brings urine from the bladder to the outside of the body, thins. A small number of women may experience an increase in urinary tract infections (UTIs) that can be improved with the use of vaginal estrogen therapy.
Perimenopause: The Menopause Transition
Other physical and emotional changes are associated with fluctuating estrogen levels during the transition to menopause and the year after menopause occurs, called perimenopause. This phase typically lasts about five years for most women. Symptoms include:
Hot flashes — a sudden sensation of heat in your face, neck and chest that may cause you to sweat profusely, increase your pulse rate and make you feel dizzy or nauseous. A hot flash typically lasts about three to six minutes, although the sensation can last longer and may disrupt sleep when they occur at night.
Irregular menstrual cycles
Exacerbation of migraines
Urinary stress incontinence
Estrogen therapy is used to treat certain conditions, such as delayed onset of puberty and menopausal symptoms such as hot flashes and symptomatic vaginal atrophy. Vaginal atrophy is a condition in which low estrogen levels cause a woman’s vagina to narrow, lose flexibility and take longer to lubricate. Female hypogonadism or incomplete functioning of the ovaries, can also cause vaginal dryness, breast atrophy and lower sex drive, and is also treated with estrogen.
For many years, estrogen therapy and estrogen-progestin therapy were prescribed to treat menopausal symptoms, to prevent osteoporosis and to improve women’s overall health. However, after publication of results from the Women’s Health Initiative (WHI) in July 2002 and March 2004, the U.S. Food and Drug Administration (FDA) now advises health care professionals to prescribe menopausal hormone therapies at the lowest possible dose and for the shortest possible length of time to achieve treatment goals.
The WHI was a study of 27,000 women aged 50-79 taking estrogen therapy or estrogen/progesterone therapy who were followed for an average of five to six years. The study was unable to document that benefits outweighed risks when hormone therapy was used as preventive therapy.
For symptomatic menopausal women or for women with premature menopause, ET or HT remains the most effective therapy for hot flashes. For more on the WHI study and the potential risks and benefits of menopausal hormone therapy, visit www.nhlbi.nih.gov.
Determining hormone status can be important in certain settings. For instance, estrogen and other hormones are prescribed to treat reproductive health and endocrine disorders (the endocrine system is the system in the body that regulates hormone production and function).
Some uses of hormone therapy include the following situations:
Irregular menstrual cycles
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Keywords: Estrogen, hormone, hormones, hormone therapy, estrogenic hormones, pregnancy, oral contraceptives, menopause, bone loss, osteoporosis, bone mass, cholesterol, perimenopause, estrogen therapy, polycystic ovarian syndrome, genital atrophy, hot flashes, vaginal dryness, women’s health initiative, chemical messenger
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