Estrogen

Estrogen is a female sex hormone produced by the ovaries, the adrenal glands, and body fat. It is responsible for the development and maintenance of female secondary sexual characteristics, such as the breasts. It also helps to maintain health in other parts of the body, including the heart, brain, bone, and liver.

Other Names

• Conjugated estrogens
• Esterified estrogens
• Estradiol
• Estropipate

Brand Names

• Cenestin
• Enjuvia
• Estrace
• Femtrace
• Gynodiol
• Menest
• Ogen
• Premarin

Uses

Estrogen therapy

Hormone therapy with estrogen may be used in the following situations.

• Delayed puberty
• Contraception (preventing pregnancy)
• Cancer symptom treatment
• Irregular menstrual cycles
• Symptomatic menopause, such as hot flashes and 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.

In addition to treating menopause-related symptoms, estrogen and other hormones are prescribed to treat reproductive health and endocrine disorders (the endocrine system regulates hormone production and function).

How Estrogen Is Taken

Estrogen is available as a tablet to take by mouth. It is usually taken once a day, with or without food. Estrogen is sometimes taken every day and sometimes taken according to a rotating schedule that alternates a period of time when estrogen is taken every day with a period of time when estrogen is not taken. When estrogen is used to relieve the symptoms of cancer, it is usually taken three times a day.

Estrogen can also be taken in several other forms.

• Cream
• Pessary
• Estradiol-releasing vaginal ring

How It Works

Estrogen is a type of female hormone. 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 human growth, development, tissue function, sexual function, the way the body uses food, the body's response to emergencies, and even moods.

The estrogenic hormones are uniquely responsible for the growth and development of female sexual characteristics and reproduction. The term "estrogen" includes a group of chemically similar hormones: estrone, estradiol (the most abundant) and estriol.

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 (estrogen and progesterone) 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 cause the production of a very thin uterine lining, called the endometrium, which is unreceptive to a fertilized egg. They also thicken the mucus on the cervix 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.

Benefits

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.

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. Estrogen creams and pessaries and estradiol-releasing vaginal rings can reduce this vaginal atrophy.^[1]

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.^[2]

Perimenopause: the menopause transition

Other physical and emotional changes are associated with fluctuating estrogen levels during the transition to menopause (the time of life when a woman stops having periods) and the year after menopause occurs, called perimenopause. This phase typically lasts about five years for most women. Symptoms of menopause include the following.

• Hot flashes, which are sudden sensations of heat in the face, neck and chest that may cause sweating, increased pulse rate, dizziness or nausea. A hot flash typically lasts about three to six minutes, although the sensation can last longer and may disrupt sleep when occurring at night.
• Irregular menstrual cycles
• Breast tenderness
• Worsening of migraines
• Urinary stress incontinence
• Mood swings

Side Effects

Estrogen may cause side effects such as:

• Breast pain or tenderness
• Upset stomach
• Vomiting
• Heartburn
• Constipation
• Diarrhea
• Gas
• Weight gain or loss
• Leg cramps
• Nervousness
• Depression
• Dizziness
• Burning or tingling in the arms or legs
• Tight muscles
• Hair loss
• Unwanted hair growth
• Spotty darkening of the skin on the face
• Difficulty wearing contact lenses
• Swelling, redness, burning, itching, or irritation of the vagina
• Vaginal discharge
• Change in sexual desire
• Cold symptoms
• Spider angiomata (small red spots on the face, trunk, arms, or back)

Some side effects can be serious:

• Bulging eyes
• Sore throat, fever, chills, cough, and other signs of infection
• Loss of appetite
• Weakness
• Yellowing of the skin or eyes
• Joint pain
• Movements that are difficult to control
• Rash or blisters
• Hives
• Itching
• Swelling of the eyes, face, tongue, throat, hands, arms, feet, ankles, or lower legs
• Hoarseness
• Difficulty breathing or swallowing

• Estrogen may cause growth to slow or stop early in children who take large doses for a long time.
• Estrogen may also affect the timing and speed of sexual development in children.

Overdose

In case of overdose, it is important to call the local poison control center at 1-800-222-1222.

Symptoms of overdose may include:

• Upset stomach
• Vomiting
• Vaginal bleeding

Controversy

The Women's Health Initiative (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, and research was halted early to minimize perceived risk to the women in the study. Many doctors advised women to stop taking estrogen after this study was published in 2002.^[3]

In 2003, The National Cancer Institute found a decrease in the rate of hormone-dependent breast cancers among women, the most common breast cancer.

In a study published in late 2006, 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.^[4]

The researchers suggested that stopping the treatment prevented very tiny cancers from growing into tumors large enough to be identified by mammogram or touch because they didn't have the additional estrogen required to fuel their growth.

The WHI has fueled a tremendous amount of discussion about whether the study should have been stopped early and whether the statistics the study collected were properly interpreted. For example, women of all ages were grouped together in the statistical analysis, which may have skewed the results.^[5]

References

1. ↑ Nothnagle M, Taylor JS. Vaginal estrogen preparations for relief of atrophic vaginitis. Am Fam Physician. 2004 May 1;69(9):2111-2. Full Text
2. ↑ Raz R, Stamm WE. A controlled trial of intravaginal estriol in postmenopausal women with recurrent urinary tract infections. N Engl J Med. 1993 Sep 9;329(11):753-6. Abstract | Full Text
3. ↑ Bush TM, Bonomi AE, Nekhlyudov L, Ludman EJ, Reed SD, Connelly MT, Grothaus LC, LaCroix AZ, Newton KM. How the Women's Health Initiative (WHI) influenced physicians' practice and attitudes. J Gen Intern Med. 2007 Sep;22(9):1311-6. Epub 2007 Jul 18. Abstract
4. ↑ Ravdin PM, Cronin KA, Howlader N et al. The decrease in breast-cancer incidence in 2003 in the United States. N Engl J Med. 2007 Apr 19;356(16):1670-4. Abstract | [Full Text]
5. ↑ Utian WH. NIH and WHI: time for a mea culpa and steps beyond. Menopause. 2007 Nov-Dec;14(6):1056-9. Abstract

External Links

National Heart, Lung, and Blood Institute: The Women's Health Initiative. This site gives more information on the WHI study and offers guidelines for considering menopausal hormone therapy and its potential risks and benefits.

Related Accredited Articles

1. Ask the Doctor Q&A: Hormone Treatment
2. Content from Harvard Medical School