What Are Selective Estrogen Receptor Modulators (SERMs)?
Key takeaways:
Selective estrogen receptor modulators (SERMs) are a group of medications that affect estrogen. They can block estrogen in some areas of your body, but help it in others.
SERMs can be used to treat a variety of health conditions, such as breast cancer and osteoporosis. Common examples of SERMs are tamoxifen (Soltamox), raloxifene (Evista), and clomiphene.
SERMs can cause side effects like mood swings and hot flashes. But more serious side effects are also possible.
Selective estrogen receptor modulators, also known as SERMs, are a class of medications that affect estrogen in your body. They’re a large and familiar group of medications that have been around for decades, and they’re used to treat a variety of estrogen-related health conditions.
But how exactly do they affect your hormones, and when might they come in handy? If you or a loved one have a health condition that’s affected by too much — or too little — estrogen, perhaps a SERM has been the subject of your attention.
Here, we'll discuss how SERMs work and how they affect your body. We’ll also look at some side effects to watch out for.
What are selective estrogen receptor modulators (SERMs) used for?
Selective estrogen receptor modulators (SERMs) are a group of synthetic (human-made) hormonal medications. They’re commonly prescribed to treat health conditions like osteoporosis after menopause, breast cancer, and menopause symptoms.
Common SERM medications include:
Tamoxifen (Soltamox). Tamoxifen is often used to treat estrogen receptor-positive (ER-positive) breast cancer. This is a type of breast cancer that uses estrogen to grow.
Raloxifene (Evista). Raloxifene is commonly prescribed for osteoporosis, but it can also be used for breast cancer risk reduction.
Bazedoxifene and conjugated equine estrogens (Duavee). Duavee can be used for osteoporosis prevention. It’s also used to help relieve menopause symptoms, like vaginal dryness and hot flashes.
Ospemifene (Osphena). Osphena is used for vaginal dryness and painful sexual intercourse in women who have gone through menopause.
Clomiphene. Clomiphene can be used to help women who haven’t gone through menopause who are experiencing infertility. It can help induce ovulation.
Toremifene (Fareston). Toremifene is used for treatment of metastatic ER-positive breast cancer.
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Are medications like anastrozole also considered SERMs?
No. Medications like anastrozole are in a different medication class called aromatase inhibitors (AIs). Aromatase inhibitors are a type of hormone therapy used for treating ER-positive breast cancer.
SERMS and AIs are somewhat similar, so they’re sometimes confused for each other. But AIs work differently than SERMs, and they aren’t used interchangeably. AIs lower the amount of estrogen in your body by blocking an enzyme (protein) called aromatase. Aromatase is needed to convert androgens (hormones like testosterone) into estrogen.
Examples of AIs include letrozole (Femara), anastrozole (Arimidex), and exemestane (Aromasin).
How do SERMs work?
SERMs work by either blocking or activating estrogen in your body. Estrogen receptors (chemical binding sites) respond differently to estrogen in different parts of the body.
Some SERMs affect estrogen receptors in your breasts and bones, while others affect your uterus. This means that SERMs are “selective” in where they work. This is why SERMs can be used for a variety of health conditions.
Let’s go through a few examples.
Breast cancer
SERMs can bind to estrogen receptors in breast cells. This stops your body’s own natural estrogen from attaching to them. Since SERMs occupy the estrogen receptor instead of natural estrogen, the cancer’s fuel source is cut off. This prevents cancer from growing and spreading.
Osteoporosis
SERMs can activate estrogen receptors in the bones. Normally, estrogen helps women build and maintain strong bones. But after menopause, estrogen levels in the body can drop. This can lead to a loss of bone density, and even osteoporosis.
SERMs can make a difference by mimicking estrogen in the bones and activating the beneficial effects of estrogen. This can improve bone density and lower the risk of bone fractures.
Fertility
Clomiphene is a SERM that blocks estrogen production. It stimulates your pituitary gland to release more follicle-stimulating hormone and luteinizing hormone in your ovaries. This process is important in regulating ovulation and menstruation in women. This can help stimulate your ovaries to release an egg.
How effective are SERMs?
A SERM’s effectiveness varies for each condition it’s being used to treat. Here, we’ll discuss breast cancer and osteoporosis more in-depth.
Prevention and treatment of breast cancer
Tamoxifen and raloxifene can be used to prevent breast cancer in some women who are at a high risk of developing it. The effect of these medications on breast cancer risk has varied in different studies, but the overall reduction in risk is about 40%.
For breast cancer treatment, a large meta-analysis studied tamoxifen for 5 years in women with breast cancer. The results of this study showed that taking tamoxifen for 5 years resulted in a significant reduction in the risk of breast cancer coming back. There was also a significant reduction in the risk of death from breast cancer after 15 years.
Prevention and treatment of osteoporosis
In a large study, more than 7,000 women with osteoporosis received either raloxifene or placebo (a pill with no medication in it) every day. Raloxifene was shown to raise bone mineral density (BMD) at the lower spine and the top of the femur by about 2% to 3% compared to placebo. Women in the study who received raloxifene also had a lower risk of vertebral fracture compared to placebo.
And as mentioned, tamoxifen is a SERM used for the prevention and treatment of breast cancer. It’s not typically used for osteoporosis, but women who have gone through menopause and are taking tamoxifen for breast cancer may also benefit from bone protection effects.
How long should you take a SERM for?
How long you take a SERM depends on what you’re using it for.
For people taking tamoxifen, or another SERM for breast cancer treatment, the general recommendation is to take it for at least 5 years. But some people take it for up to 10 years. The length of treatment is often dependent on the characteristics of your breast cancer. Your healthcare provider may also recommend taking tamoxifen for a certain period of time and then switching to different hormone therapy, like an AI.
For people taking raloxifene for osteoporosis, there’s a similar recommendation. Data from studies have shown that raloxifene is safe and effective to take for up to 8 years.
You should talk with your healthcare provider about the length of therapy with a SERM that works best for you and is most appropriate for the condition you are treating.
What are the side effects and risks of SERMs?
Like you may expect, specific SERM side effects vary by medication. But some of the more common side effects are:
Hot flashes
Night sweats
Vaginal discharge
Leg cramps
Irregular menstrual periods for women who haven’t gone through menopause yet
However, more serious side effects are also possible. Some of these serious side effects are also described as boxed warnings. A boxed warning is the most serious warning that the FDA can give to a medication.
For instance, tamoxifen has boxed warnings for uterine cancer and blood clots. Raloxifene has boxed warnings for blood clots and strokes. Duavee has boxed warnings for dementia, endometrial cancer, and certain heart problems. Osphena has boxed warnings for endometrial cancer and certain heart problems.
How much do SERMs cost?
SERMs vary in cost. But many of them have generic versions available that are relatively affordable. The table below shows how much you can expect to pay for a 1-month supply of each SERM.
| Medications | Average retail price | GoodRx price |
|---|---|---|
| Tamoxifen | $73 | As low as $17 |
| Raloxifene | $197 | As low as $13 |
| Duavee (no generic available) | $242 | As low as $180 |
| Osphena (no generic available) | $289 | As low as $234 |
| Clomiphene | $104 | As low as $20 |
| Toremifene | $997 | As low as $325 |
There are also other ways to save. If you have prescription insurance, your plan may help cover part or all of your medication’s cost. For specific coverage information, it’s recommended to reach out to your plan provider for details.
The bottom line
SERMs are a unique class of medications that have different effects on estrogen in your body. They can be effective for treating a variety of estrogen-related health conditions. The most common SERMs are tamoxifen and raloxifene, but others are also available. To determine if treatment with a SERM is right for you, it’s recommended to speak with your healthcare provider.
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References
Actavis Pharma, Inc. (2022). Tamoxifen [package insert].
An, K. C. (2016). Selective estrogen receptor modulators. Asian Spine Journal.
American Cancer Society. (2020). Hormone therapy.
American Cancer Society. (2021). Tamoxifen and raloxifene for lowering breast cancer risk.
Breastcancer.org. (2022). Hormone receptor status.
Bryant Ranch Prepack. (2022). Raloxifene [package insert].
Early Breast Cancer Trialists' Collaborative Group (EBCTCG). (2011). Relevance of breast cancer hormone receptors and other factors to the efficacy of adjuvant tamoxifen: Patient-level meta-analysis of randomised trials. Lancet.
Endocrine Society. (2022). Reproductive hormones.
Ettinger, B., et al. (1999). Reduction of vertebral fracture risk in postmenopausal women with osteoporosis treated with raloxifene: Results from a 3-year randomized clinical trial. JAMA.
Fisher, B., et al. (2005). Tamoxifen for the prevention of breast cancer: Current status of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. Journal of the National Cancer Institute.
Jordan, V. C., et al. (2004). Selective estrogen receptor modulation: Concept and consequences in cancer. Cancer Cell.
Maximov, P. Y., et al. (2013). The discovery and development of selective estrogen receptor modulators (SERMs) for clinical practice. Current Clinical Pharmacology.
Mbi Feh, M. K., et al. (2022). Clomiphene. StatPearls.
National Cancer Institute. (n.d.). Selective estrogen receptor modulator.
National Comprehensive Cancer Network. (2020). NCCN guidelines for patients invasive breast cancer.
Peters, A., et al. (2021). Aromatase inhibitors. StatPearls.
Pharma Packaging Solutions. (2022). Osphena [package insert].
Quintanilla Rodriguez, B. S., et al. (2021). Raloxifene. StatPearls.
Siris, E. S., et al. (2009). Skeletal effects of raloxifene after 8 years: Results from the continuing outcomes relevant to Evista (CORE) study. Journal of Bone and Mineral Research.
U.S. Pharmaceuticals. (2021). Duavee [package insert].
U.S. Preventive Services Task Force. (2019). Medication use to reduce risk of breast cancer: US Preventive Services Task Force recommendation statement. JAMA.
