Estrogen Replacement Therapy (ERT)

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Estrogen Replacement Therapy (ERT)


Oral (pills or tablets)

Generic NameBrand Name
conjugated estrogensC.E.S., Congest, Premarin
Generic NameBrand Name
esterified estrogensNeo Estrone

Transdermal (patch placed on the skin that releases estrogen continuously)

Generic NameBrand Name
estradiolClimera, Estraderm

Vaginal ring (inserted high into the vagina; releases estrogen continuously for 3 months)

Generic NameBrand Name

Skin gel (applied daily to an arm from wrist to shoulder)

Generic NameBrand Name

How It Works

Estrogen replacement therapy (ERT) increases the estrogen level in your body. Estrogen impacts multiple systems of the body.

When given through an estrogen patch, vaginal ring, or gel (transdermal estrogen), estrogen enters the bloodstream directly, without passing through the liver. The estrogen in pills must be processed by the liver before entering the bloodstream, which puts stress on an impaired liver.

Low-dose vaginal estrogen affects only the urinary and genital area. For more information, see Low-Dose Vaginal Estrogen for Dryness and Atrophy.

Patch warning. Direct sunlight or high heat can increase, then decrease, the amount of hormone released from a patch. This can give you a big dose at the time and leave less hormone for the patch to release later in the week. Avoid direct sunlight on the hormone patch. Also avoid using a tanning bed, heating pad, electric blanket, hot tub, or sauna while you are using a hormone patch.

Why It Is Used

Estrogen replacement therapy (ERT) is used to increase estrogen levels in postmenopausal women who have no uterus. This treatment may help prevent perimenopausal symptoms, osteoporosis, and colon cancer.

Women in their 20s, 30s, and 40s who experience early menopause after having their ovaries removed (oophorectomy) or because of other medical reasons typically take ERT to reduce their risk of early bone loss and osteoporosis. Historically, women have continued using ERT for years beyond menopause. Some women now discontinue ERT around the age of menopause.

Women with a uterus who take estrogen also need the hormone progestin to prevent the estrogen from overgrowing the uterine lining, which can lead to endometrial (uterine) cancer. Estrogen-progestin is called hormone replacement therapy (HRT).

Do not use estrogen treatment if you:

  • Are pregnant.
  • Have unexplained vaginal bleeding.
  • Have active liver disease or chronic impaired liver function. (Transdermal estrogen does not stress the liver.)
  • Have a personal history of breast cancer, ovarian cancer, or endometrial cancer.
  • Are a smoker.
  • Have a history of blood clots.
  • Have had a stroke.

Talk to your doctor about your risks versus benefits if you have a family history of breast cancer, ovarian cancer, stroke, blood clots, or endometrial cancer.

How Well It Works

Systemic estrogen replacement therapy (ERT) affects your entire body and reverses the effect of low estrogen. Systemic ERT may:

  • Reduce the frequency and severity of hot flashes.4
  • Improve moodiness and sleep problems related to hormone changes.1
  • Maintain the lining of the vagina, reducing irritation.
  • Increase skin collagen levels, which decline as estrogen levels decline. Collagen is responsible for the stretch in skin and muscle.
  • Help prevent post-menopausal osteoporosis by slowing bone loss and promoting some increase in bone density.4
  • Reduce the risk of dental problems, such as tooth loss and gum disease.

Low-dose estrogen. Researchers are studying the effects of low-dose estrogen therapy. Low-dose estrogen may keep bones strong and may relieve hot flash symptoms.5 But the long-term risks of taking low-dose estrogen are not yet known.

Side Effects

Risks of estrogen replacement therapy

Estrogen replacement therapy (ERT) may increase the risk of health problems in a small number of women. This increase in risk depends on your age, your personal risk, and when ERT is started.1 Talk with your doctor about these risks. Using ERT may increase your risk of:

  • Stroke.
  • Blood clots.
  • Breast cancer.
  • Gallstones.
  • Ovarian cancer.
  • Dementia.

Side effects that can occur with all forms of estrogen but are more common with oral estrogen (and less common with a patch, gel, or vaginal ring) include:

  • Headaches.
  • Nausea.
  • Vaginal discharge.
  • Fluid retention.
  • Weight gain.
  • Breast tenderness.
  • Spotting or darkening of the skin, particularly on the face.
  • In rare cases, an increased growth of preexisting uterine fibroids or a worsening of endometriosis.

Some of these side effects, such as headaches, nausea, fluid retention, weight gain, and breast tenderness, may go away after a few weeks of use.

The estrogen patch (transdermal estrogen) may cause skin irritation.

An estrogen ring must be replaced every 3 months. If the ring falls out at any time during the 3-month treatment period, you may rinse it with lukewarm water and reinsert it.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

In the Million Women Study of British women ages 50 to 64, taking any form of estrogen for 10 years increased breast cancer risk. The Women's Health Initiative study did not show this increased risk for women taking estrogen alone (ERT) for 7 years.3 So taking long-term ERT probably slightly increases breast cancer risk, and taking it with progestin (HRT) further increases breast cancer risk.2 But only women who have had a hysterectomy can take estrogen alone without also worrying about endometrial (uterine) cancer risk.2

ERT use slightly increases the risk of stroke. For this reason, the Women's Health Initiative ERT trial was stopped sooner than originally planned. In this large trial, women using ERT had no change in heart disease risk, had fewer hip fractures (a sign of estrogen's bone-protecting effect), and (unlike the larger Million Women Study) had no increase in breast cancer risk during the study's nearly 7 years of ERT treatment.3

If you are taking ERT after early menopause caused by a surgical hysterectomy, talk with your doctor about long-term ERT risks and benefits.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.



  1. North American Menopause Society (2010). Estrogen and progestogen use in postmenopausal women: 2010 position statement of the North American Menopause Society. Menopause, 17(2): 242–255. Also available online:
  2. Million Women Study Collaborators (2003). Breast cancer and hormone-replacement therapy in the Million Women Study. Lancet, 362(9382): 419–427.
  3. Women's Health Initiative Steering Committee (2004). Effects of conjugated equine estrogen in postmenopausal women with hysterectomy. JAMA, 291(14): 1701–1712.
  4. Speroff L, Fritz MA (2005). Menopause and the perimenopausal transition. In Clinical Gynecologic Endocrinology and Infertility, 7th ed., pp. 621–688. Philadelphia: Lippincott Williams and Wilkins.
  5. Bachmann GA, et al. (2007). Lowest effective transdermal 17beta-estradiol dose for relief of hot flashes in postmenopausal women. Obstetrics and Gynecology, 110(4): 771–779.


By Healthwise Staff
Primary Medical Reviewer Kathleen Romito, MD - Family Medicine
Primary Medical Reviewer Brian D. O'Brien, MD - Internal Medicine
Specialist Medical Reviewer Carla J. Herman, MD, MD, MPH - Geriatric Medicine
Last Revised June 30, 2010

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