Table of ContentsView AllTable of ContentsTypesBenefitsSide EffectsAre SERMs Safe?Frequently Asked Questions

Table of ContentsView All

View All

Table of Contents

Types

Benefits

Side Effects

Are SERMs Safe?

Frequently Asked Questions

Selective estrogen receptor modulators (SERMs) are a group of medications classified as hormone therapies. Two common SERMs are Nolvadex (tamoxifen) for the treatment of breast cancer and Evista (raloxifene) forosteoporosis(progressive bone thinning).

These medications act on a protein in some cells of the body called the estrogen receptor. The estrogen receptor binds to the hormoneestrogen, sending a signal to the cell. This signal causes the cells to grow and can exert other effects.

This article will explain selective estrogen receptor modulators, how they work, what they are, and the most common kinds. It will also discuss side effects and safety and how healthcare providers prescribe them for osteoporosis, breast cancer, and other conditions.

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Person with breast cancer consults telehealth provider about SERMs

Estrogen

The ovaries (egg-producing organs) release the hormone estrogen during the menstrual cycle, as do the adrenal glands, fat, and skin. During pregnancy, the placenta releases estrogen. Estrogen can impact tissues differently based on how their cells are programmed to react to it.

Estrogen affects the growth of mammary tissue, hair growth, and the menstrual cycle. Whenestrogen is too highor too low, menstrual periods may be irregular, and mood, bone health, and heart health can be affected.

Estrogen is also an important factor fueling the growth of some breast cancers and is important in growing long bones, like the limb bones.

Estrogen Modulators

Compounds that act as “modulators” can attach to the estrogen receptor to change its activity. For example, SERMs are modulators for some estrogen receptors—turning up or down the effects of estrogen through binding to its receptor.

In some tissues, including breast tissue, SERMs block the effects of estrogen. In others, they act like estrogen, binding the receptor. Different SERMs are active in various tissues.

When estrogen changes in the body lead to an illness, SERMs may be a treatment option. These illnesses includeestrogen receptor-positive (ER+) breast cancers, osteoporosis, andmenopause(the cessation of menstruation).

Types of SERM Drugs

The differences between SERMS come down to what tissues they act upon and if they also mimic estrogen in some tissues. These differences play a role in who gets prescribed these medications and for which conditions.

Tamoxifen (Nolvadex, Soltamox)

Tamoxifenis a SERM used as hormone therapy to treat breast cancer. It’s primarily used in people of any sex whose cancer has spread to other body parts and in females with early breast cancer after other therapies.

For people withstage 0 breast cancer(ductal carcinoma in situ) Tamoxifen can help reduce the risk of developing a more serious type of breast cancer.

Raloxifene (Evista, Keoxifene)

Other Less Common SERMs

Less common SERMs include:

Benefits of SERMs

When used in the right treatment groups, SERMs can improve bone density in people with osteoporosis, reduce the likelihood of some fractures due to low bone density, and reduce the risk that breast cancer will develop or come back after treatment.

SERMs for Osteoporosis

SERMs for Breast Cancer

Tamoxifen, as hormone therapy, cantreat ER+ breast cancer. In the cancer cells, tamoxifen stops estrogen from binding to the receptor, stopping the signal telling cancer to grow.

People being treated for breast cancer typically take the drug after surgery and other treatments, typically for five years and sometimes longer. Healthcare providers will sometimes prescribe toremifene in place of tamoxifen.

SERMs for Other Conditions

Some SERMs—specifically bazedoxifene—are combined with a mixture of estrogens (called conjugated estrogens) to treat moderate-to-severehot flashesand othervasomotor symptoms of menopause(temperature dysfunction).

The SERM selectively blocks the estrogens from impacting the uterus, reducing the likelihood that the estrogens will lead to cancer.

SERMs vs. Aromatase Inhibitors

SERMS are similar to another class of drugs called aromatase inhibitors. Aromatase inhibitors are another type of hormone therapy. They are used more often for people who have gone through menopause.

Aromatase inhibitors act to stop estrogen from being made, decreasing the amounts of and effects of this hormone in the body.

Common aromatase inhibitors used to treat breast cancer include:

Side Effects of SERMs

Because they act on estrogen receptors, SERMs mimic menopause in people who menstruate. Side effects of SERMs may include symptoms of menopause. These can include:

Other more dangerous side effects can happen but are rare. These include blood clots—known asdeep vein thrombosisin the leg andpulmonary embolismin the lungs—leading to serious problems and even death.

Raloxifene Side Effects

Raloxifene may cause side effects. These can include:

Mention these symptoms to your healthcare provider if they are severe or do not go away.

Tamoxifen Side Effects

While tamoxifen has been a game-changing drug for breast cancer care, there are some possible side effects you should be aware of.

Tumor flare: If you’re taking tamoxifen as a treatment for cancer that has spread to the bones, you may experience a tumor flare, in which the tumor gets bigger for a short time and causes bone pain. The tumor flare can lead to a high calcium level in the blood that is hard to control.

Uterine cancer: Some SERMs increase the risk of developing uterine cancer and endometrial pre-cancers. Tell your healthcare provider if you have vaginal bleeding, pelvic pain or pressure, irregular periods, or unusual vaginal discharge, especially if you’re post-menopausal.

Signs of Uterine CancerIf you are taking tamoxifen, tell your healthcare provider if you have any abnormal vaginal bleeding or spotting, especially after menopause, as these are possible symptoms of uterine cancer.

Signs of Uterine Cancer

If you are taking tamoxifen, tell your healthcare provider if you have any abnormal vaginal bleeding or spotting, especially after menopause, as these are possible symptoms of uterine cancer.

Other common side effects of tamoxifen can include:

Mention these symptoms to your healthcare provider if severe or do not go away.

Side Effects of Toremifene

Toremifene may cause QT prolongation (an irregular heart rhythm that can lead to fainting, loss of consciousness, seizures, or sudden death).

Other side effects of toremifene include:

SERMs are generally safe for use according to prescribing guidelines. The risk of developing more dangerous side effects like uterine cancer or blood clots is relatively low:

Summary

Selective estrogen receptor modulators (SERMs) are a class of drugs that impact the action of estrogen and the estrogen receptors in the body. They can prevent breast cancer and treat it and osteoporosis. They’re generally safe but may have some serious or mild side effects.

Frequently Asked QuestionsSERM stands for selective estrogen receptor modulators, which means these drugs act on the estrogen receptor. They don’t change the estrogen level in the body but can impact how the body responds to the hormone.Learn MoreHormone Therapy for Breast CancerPeople with dense breast tissue have more connective tissue than fatty tissue. Dense breast tissue puts them at a higher risk of developing breast cancer.Therapy with tamoxifen can reduce breast density, potentially lowering the risk of breast cancer.Learn MoreDense Breasts and Breast Cancer Risk

SERM stands for selective estrogen receptor modulators, which means these drugs act on the estrogen receptor. They don’t change the estrogen level in the body but can impact how the body responds to the hormone.Learn MoreHormone Therapy for Breast Cancer

SERM stands for selective estrogen receptor modulators, which means these drugs act on the estrogen receptor. They don’t change the estrogen level in the body but can impact how the body responds to the hormone.

Learn MoreHormone Therapy for Breast Cancer

People with dense breast tissue have more connective tissue than fatty tissue. Dense breast tissue puts them at a higher risk of developing breast cancer.Therapy with tamoxifen can reduce breast density, potentially lowering the risk of breast cancer.Learn MoreDense Breasts and Breast Cancer Risk

People with dense breast tissue have more connective tissue than fatty tissue. Dense breast tissue puts them at a higher risk of developing breast cancer.Therapy with tamoxifen can reduce breast density, potentially lowering the risk of breast cancer.

Learn MoreDense Breasts and Breast Cancer Risk

13 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.American Cancer Society.Tamoxifen and raloxifene for lowering breast cancer risk.National Cancer Institute.Definition of estrogen receptor.National Cancer Institute.Definition of estrogen.National Cancer Institute.Definition of selective estrogen receptor modulator.MedlinePlus.Tamoxifen.MedlinePlus.Raloxifene.MedlinePlus.Toremifene.Lainé M, Fanning SW, Chang YF, et al.Lasofoxifene as a potential treatment for therapy-resistant ER-positive metastatic breast cancer.Breast Cancer Res. 2021;23(1):54. doi:10.1186/s13058-021-01431-wMartinkovich S, Shah D, Planey SL, Arnott JA.Selective estrogen receptor modulators: tissue specificity and clinical utility.Clin Interv Aging. 2014;9:1437-1452. doi:10.2147/CIA.S66690An KC.Selective estrogen receptor modulators.Asian Spine J. 2016;10(4):787-791. doi:10.4184/asj.2016.10.4.787MedlinePlus.Estrogen and bazedoxifene.American Cancer Society.Hormone therapy for breast cancer.American Cancer Society.Breast density and your mammogram report.Additional ReadingAmerican Cancer Society.Tamoxifen and raloxifene for lowering breast cancer risk.An KC.Selective estrogen receptor modulators.Asian Spine J. 2016;10(4):787-791. doi:10.4184/asj.2016.10.4.787

13 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.American Cancer Society.Tamoxifen and raloxifene for lowering breast cancer risk.National Cancer Institute.Definition of estrogen receptor.National Cancer Institute.Definition of estrogen.National Cancer Institute.Definition of selective estrogen receptor modulator.MedlinePlus.Tamoxifen.MedlinePlus.Raloxifene.MedlinePlus.Toremifene.Lainé M, Fanning SW, Chang YF, et al.Lasofoxifene as a potential treatment for therapy-resistant ER-positive metastatic breast cancer.Breast Cancer Res. 2021;23(1):54. doi:10.1186/s13058-021-01431-wMartinkovich S, Shah D, Planey SL, Arnott JA.Selective estrogen receptor modulators: tissue specificity and clinical utility.Clin Interv Aging. 2014;9:1437-1452. doi:10.2147/CIA.S66690An KC.Selective estrogen receptor modulators.Asian Spine J. 2016;10(4):787-791. doi:10.4184/asj.2016.10.4.787MedlinePlus.Estrogen and bazedoxifene.American Cancer Society.Hormone therapy for breast cancer.American Cancer Society.Breast density and your mammogram report.Additional ReadingAmerican Cancer Society.Tamoxifen and raloxifene for lowering breast cancer risk.An KC.Selective estrogen receptor modulators.Asian Spine J. 2016;10(4):787-791. doi:10.4184/asj.2016.10.4.787

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

American Cancer Society.Tamoxifen and raloxifene for lowering breast cancer risk.National Cancer Institute.Definition of estrogen receptor.National Cancer Institute.Definition of estrogen.National Cancer Institute.Definition of selective estrogen receptor modulator.MedlinePlus.Tamoxifen.MedlinePlus.Raloxifene.MedlinePlus.Toremifene.Lainé M, Fanning SW, Chang YF, et al.Lasofoxifene as a potential treatment for therapy-resistant ER-positive metastatic breast cancer.Breast Cancer Res. 2021;23(1):54. doi:10.1186/s13058-021-01431-wMartinkovich S, Shah D, Planey SL, Arnott JA.Selective estrogen receptor modulators: tissue specificity and clinical utility.Clin Interv Aging. 2014;9:1437-1452. doi:10.2147/CIA.S66690An KC.Selective estrogen receptor modulators.Asian Spine J. 2016;10(4):787-791. doi:10.4184/asj.2016.10.4.787MedlinePlus.Estrogen and bazedoxifene.American Cancer Society.Hormone therapy for breast cancer.American Cancer Society.Breast density and your mammogram report.

American Cancer Society.Tamoxifen and raloxifene for lowering breast cancer risk.

National Cancer Institute.Definition of estrogen receptor.

National Cancer Institute.Definition of estrogen.

National Cancer Institute.Definition of selective estrogen receptor modulator.

MedlinePlus.Tamoxifen.

MedlinePlus.Raloxifene.

MedlinePlus.Toremifene.

Lainé M, Fanning SW, Chang YF, et al.Lasofoxifene as a potential treatment for therapy-resistant ER-positive metastatic breast cancer.Breast Cancer Res. 2021;23(1):54. doi:10.1186/s13058-021-01431-w

Martinkovich S, Shah D, Planey SL, Arnott JA.Selective estrogen receptor modulators: tissue specificity and clinical utility.Clin Interv Aging. 2014;9:1437-1452. doi:10.2147/CIA.S66690

An KC.Selective estrogen receptor modulators.Asian Spine J. 2016;10(4):787-791. doi:10.4184/asj.2016.10.4.787

MedlinePlus.Estrogen and bazedoxifene.

American Cancer Society.Hormone therapy for breast cancer.

American Cancer Society.Breast density and your mammogram report.

American Cancer Society.Tamoxifen and raloxifene for lowering breast cancer risk.An KC.Selective estrogen receptor modulators.Asian Spine J. 2016;10(4):787-791. doi:10.4184/asj.2016.10.4.787

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