Estrogen; Overview

Estrogen; Overview

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

Bone

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

Breast tenderness

Exacerbation of migraines

Urinary stress incontinence

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 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:

Delayed puberty

Contraception

Irregular menstrual cycles

Symptomatic menopause

References

Effects of Estrogen plus Progestin on Health-Related Quality of Life. J. Hays et al. NEJM, May 8,2003; Vol. 348, No. 19.

FDA Approves Lower Dose of Prempro, A Combination Estrogen and Progestin Drug for Postmenopausal Women. Press Release, March 13, 2003. http://www.fda.gov

Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results From the Women’s Health Initiative randomized controlled trial. JAMA. 2002 Jul 17;288(3):321-33.

FDA Orders Warning on all Estrogen Labels. New York Times. Jan. 9, 2003

FDA Approves new Labels for Estrogen and Estrogen with Progestin Therapies for Postmenopausal Women Following Review of Women’s Health Initiative Data. FDA Talk Paper. Jan. 8, 2003.

“Precocious Puberty” The Nemours Foundation. Reviewed Aug. 2000. http://kidshealth.org. Accessed Sept. 2002.

“Estrogen Tests” Lab Tests Online. American Association for Clinical Chemistry. Revised Jan. 2002. http://www.labtestsonline.org. Accessed Sept. 2002.

Grady D, Herrington D, Bittner V, et al, for the HERS Research Group. Heart and estrogen/progestin replacement study follow-up (HERS II): Part 1. Cardiovascular outcomes during 6.8 years of hormone therapy. JAMA 2002;288:49-57.

Hulley S, Furberg C, Barrett-Connor E, et al, for the HERS Research Group. Heart and estrogen/progestin replacement study follow-up (HERS II): Part 2. Non-cardiovascular outcomes during 6.8 years of hormone therapy. JAMA 2002;288:58-66.

Writing Group for the Women’s Health Initiative Investigators. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women’s Health Initiative randomized controlled trial. JAMA 2002; 288:321-333.

Lacey, James V., et al. “Menopausal Hormone Replacement Therapy and Risk of Ovarian Cancer.” JAMA 2002. Vol. 288:334-341.368-369.

AACE Medical Guidelines For Clinical Practice For Management of Menopause. American Association of Clinical Endocrinologists. http://www.aace.com. Accessed August 2003.

Blondell, Richard, Michael Foster and Kamlesh Dave. “Disorders of Puberty.” American Family Health care professional. July 1999. Vol. 60, No. 1. pp. 209-28. Available online at http://www.aafp.org.

Carr, Bruce. “Disorders of the Ovaries and Female Reproductive Tract.” Williams Textbook of Endocrinology, 9th ed. Ed. Jean Wilson. Philadelphia: WB Saunders. 1998. pp. 751-818.

“Estrogen and Cardiovascular Diseases in Women.” American Heart Association. http://www.americanheart.org. Updated 2002. Accessed August 2003.

Estrogens and Progestins information. MEDLINEplus Health Information. National Institutes of Health (Micromedex Inc.) http://www.nlm.nih.gov. Updated July 2003. Accessed August 2003.

“Oral Contraceptives and Cancer Risk.” National Cancer Institute. http://cis.nci.nih.gov. Reviewed Feb. 12, 2003; accessed Aug. 2003.

“Postmenopausal Hormone Therapy.” National Heart, Lung and Blood Institute. http://www.nhlbi.nih.gov. Updated June 2003; accessed August 2003.

“2 Supplements Offer Questionable Relief From Menopause” Health on the Net Foundation. http://www.hon.ch. July 2003; accessed August 2003.

“Hot flashes: Treatments are available” Women’s Health Center. MayoClinic.com. http://www.mayoclinic.com. June 2003; accessed August 2003.

“Rates of Dementia Increase Among Older Women on Combination Hormone Therapy” NIH News. National Institutes of Health. http://www.nih.gov. May 27, 2003; accessed August 2003.

DiSaia, Creasman Clinical Gynecologic Oncology sixth edition. Mosby, Inc. St. Louis, 2002 The Women’s Health Initiative Participant Website. WHI Clinical Coordinating Center. May 2003. Available at: http://www.whi.org. Accessed November 2005.

Information on Enjuvia. Drugs.com. October 2005. Available at: http://www.drugs.com. Accessed November 2005.

“Effects of conjugated equine estrogens on breast cancer and mammography in postmenopausal women with hysterectomy.” The Women’s Health Initiative Participant Web site. April 2006. http://www.whi.org. Accessed May 2006.

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

COPYRIGHT 2006 National Women’s Health Resource Center

COPYRIGHT 2007 Gale Group