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Everything You Need to Know About Estrogen

Sheryl Kraft

Overview

What Is It?
Estrogen refers to a group of hormones that play an essential role in the growth and development of female sexual characteristics and the reproductive process.

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 is not entirely clear.

To understand the roles 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, metabolism, tissue function, sexual function, reproduction, the way our bodies use food, the reaction of our bodies to emergencies and even our moods.

The Role of Estrogen in Women
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 in women of reproductive age) and estriol. Overall, estrogen is produced in the ovaries, adrenal glands and fat tissues. More specifically, the estradiol and estrone forms are produced primarily in the ovaries in premenopausal women, 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 breasts 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.

Estrogen & Pregnancy
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

Bone

Estrogen produced by the ovaries helps prevent bone loss and works together with calcium, vitamin D 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 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 off 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, called perimenopause. This phase typically lasts two to eight years. Estrogen levels may continue to fluctuate in the year after menopause. 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 it occurs at night.
  • Irregular menstrual cycles
  • Breast tenderness
  • Exacerbation of migraines
  • Mood swings

Estrogen Therapy

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, a condition in which the ovaries produce little or no hormones, as well as premature ovarian failure, 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 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. Treatment is generally reserved for management of menopausal symptoms rather than prevention of chronic disease.

The WHI was a study of 27,347 women aged 50 to 79 (mean age, 63) taking estrogen therapy or estrogen/progestin therapy. They were followed for an average of five and a half to seven years. The study was unable to document that benefits outweighed risks when hormone therapy was used as preventive therapy, and it found that risk due to hormones may differ depending on a woman''s age or years since menopause.

The National Cancer Institute found a very significant drop in the rate of hormone-dependent breast cancers among women, the most common breast cancer, in 2003. In a study published in the New England Journal of Medicine in April 2007, researchers speculated that the drop was directly related to the fact that millions of women stopped taking hormone therapy in 2002 after the results of a major government study found the treatment slightly increased a woman's risk for breast cancer, heart disease and stroke. The researchers found that the decrease in breast cancer began in mid-2002 and leveled off after 2003. The decrease occurred in women over 50 and was marked in women with tumors that were estrogen receptor (ER) positive—cancers that require estrogen to grow. The researchers speculate that stopping the treatment prevented very tiny ER positive cancers from growing (and in some cases, possibly helped them to regress) because they didn't have the additional estrogen required to fuel their growth.

However, for symptomatic menopausal women or for women with premature menopause, hormone therapy remains the most effective therapy for hot flashes. For more on the WHI study, guidelines for considering menopausal hormone therapy and its potential risks and benefits, visit the .

In addition to treating menopause-related symptoms, 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:

  • delayed puberty
  • contraception
  • irregular menstrual cycles
  • symptomatic menopause

 

Diagnosis

Because hormone disorders can cause a wide variety of symptoms that also are associated with other conditions, a careful evaluation of your symptoms and general health is recommended, especially if you experience any unusual symptoms. To arrive at a diagnosis, your health care professional will want to rule out certain conditions.

Your assessment will include a thorough personal medical history, a family medical history and a physical examination. Blood and other laboratory tests may be ordered to measure hormone levels. Brain scans are sometimes ordered to identify abnormalities that may be affecting the endocrine system, and DNA testing can detect genetic abnormalities.

Estradiol or other hormone levels may be tested in the evaluation of precocious puberty in girls (the onset of signs of puberty before age seven), delayed puberty and in assisted reproductive technology (ART) to monitor ovarian follicle development in the days prior to in-vitro fertilization. Hormone levels are also sometimes used to monitor HT.

Estrone and/or estradiol levels may be tested if you are having hot flashes, night sweats, insomnia and/or amenorrhea (the absence of periods for extended periods of time). However, due to the day-to-day and even hour-to-hour fluctuations in estradiol levels, they are less helpful than follicle stimulating hormone levels (FSH) for these evaluations. Salivary estradiol testing is less reliable still and of no value in diagnosing or treating symptoms. In most cases, a woman's age, symptoms and menstrual irregularity is sufficient for making the diagnosis.

Accurate diagnosis of hormonal disorders is important to determining appropriate treatment, which often includes estrogen therapy.

The following are common reasons estrogen therapy is prescribed:

  • Delayed puberty. Delayed puberty can result from a variety of disruptions to normal hormone production, including central nervous system lesions, pituitary disorders, autoimmune processes involving the ovaries or other endocrine glands, metabolic and infectious diseases, anorexia or malnutrition, exposure to environmental toxins and over-intensive athletic training.Signs of delayed puberty include:
    • Lack of breast tissue development by the age of 13
    • No menstrual periods for five years following initial breast growth or by age 16
    • Estrogen treatment for girls with delayed puberty is somewhat controversial; some health care professionals advise treatment, while others prefer close monitoring.
  • Irregular menstrual periods. Once a medical evaluation finds that there is no other serious cause of your irregular cycles, oral contraceptives or cyclic progesterone may be used to regulate your cycle, assuming there is no reason you can't use them. Polycystic ovarian syndrome is a common cause of irregular menstrual cycles.
  • Contraception. Oral contraceptives containing estrogen are one of the most popular methods of fertility control in the United States. Other hormonal methods include some types of intrauterine devices (IUDs), the patch and an intravaginal ring.
  • Menopausal Symptoms. Declining or fluctuating levels of estrogen and other hormones such as testosterone may begin as early as the late 30s. These hormonal changes trigger many of the physical and emotional changes associated with the transition to menopause. Of course, menopause is a life stage, not a disease, but symptoms associated with menopause can be bothersome and concerning for some women.

These changes may include:

  • Irregular menstrual periods
  • Hot flashes (sudden warm feeling, sometimes with blushing or sweating)
  • Night sweats (hot flashes that occur at night, often disrupting sleep)
  • Fatigue (probably from disrupted sleep patterns)
  • Mood swings
  • Early morning awakening
  • Vaginal dryness
  • Fluctuations in sexual desire or response
  • Difficulty sleeping

There is a wide range of possible menopause-related conditions. Ask your health care professional about any changes you notice.

For symptomatic menopausal women or women with premature menopause, HT or estrogen therapy (ET) remains the gold standard for relief of hot flashes and vaginally related symptoms. The estrogen-only therapy may only be prescribed for women who have had a hysterectomy and therefore are not at risk of uterine cancer. For perimenopausal women with these symptoms, estrogen is usually given short-term (usually two to five years), with the goal of tapering and eventually discontinuing it.

If you are experiencing moderate to severe menopausal symptoms or not getting symptom relief from nonhormonal methods, hormone therapy may be an option. (To find out about alternative, nondrug methods of relieving menopausal symptoms, visit the topic at HealthyWomen.org.)

New, lower-dose versions of the hormone therapies used to treat symptoms of menopause are now available. The U.S. Food and Drug Administration (FDA) has approved pills, skin patches, gels, lotions and sprays in lower doses. Delivery of estrogen through the skin may be less likely than pills to cause blood clots in the legs or lungs.

The estrogen dosage used for hormone therapy varies widely depending on the symptoms it's intended to manage, as does dosing schedule. Discuss your symptoms and concerns with your health care professional.

In 2003, the FDA announced that a new warning on all estrogen products for use by postmenopausal women. The so-called "black box" is the strongest step the FDA can take to warn consumers of potential risks from a medication. It advises health care professionals to prescribe estrogen products at the lowest dose and for the shortest possible length of time.

While HT had also until 2002 been widely used to prevent postmenopausal osteoporosis, the health risks of hormone therapy may outweigh this benefit for many women. Other osteoporosis therapies should be considered first.

Although observational studies over many years indicated that HT prevented heart disease in postmenopausal women, the American Congress of Obstetricians and Gynecologists (ACOG), the North American Menopause Society (NAMS), and several other professional organizations say menopausal hormone therapy should not be used for primary or secondary prevention of coronary heart disease because there's not enough evidence to show long-term estrogen therapy or hormone replacement therapy improves cardiovascular outcome. However, ACOG and NAMS say women in early menopause who are in good cardiovascular health may consider estrogen plus progestin for their menopausal symptoms. Talk to your health care professional about your individual risks.