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The Role of Hormones in Breast Cancer




Breast cancer is a global concern, touching the lives of countless women. What if we could better understand its roots, specifically the role of our hormones? Continue reading as we unravel the intimate dance between hormones and breast cancer. In this article, we’ll review what hormones are commonly associated with breast cancer and differentiate between types of breast cancer and treatment based on hormone status.


What Are Hormones?

Hormones are chemical messengers produced by the endocrine glands in our body. They travel through the bloodstream to tissues and organs, influencing many bodily processes, including growth, metabolism, and reproductive functions. Among the many hormones, estrogen, progesterone, and testosterone are particularly relevant when it comes to breast cancer.


Hormonal Influence on Breast Cancer

According to the National Cancer Institute, breast cancer’s growth can sometimes be fueled by the body’s natural female hormones, particularly estrogen and progesterone. These cancer cells possess receptors on their surface, which can bind to these hormones circulating in the body. As a result, hormone receptors — proteins that pick up hormone signals — are routinely tested during a breast cancer diagnosis.


Understanding the hormone sensitivity of your breast cancer assists your doctor in determining the most effective treatment strategy or in preventing recurrence.


  • Hormone Receptor-Positive Breast Cancer: When breast cancer cells have receptors for estrogen and progesterone, they are termed ER-positive or PR-positive, respectively. They rely on these hormones to grow.


  • Hormone Receptor-Negative Breast Cancer: If breast cancer cells lack these receptors, termed ER-negative or PR-negative, they don’t rely on hormones for growth and usually require different treatment approaches.


Estrogen and Breast Cancer

Estrogen is an important hormone involved in the normal development of breast tissue. It promotes cell growth and division in the breasts and other areas of the body. However, prolonged exposure to high estrogen levels over time increases the risk of developing breast cancer.


Several factors can lead to excessive cumulative estrogen exposure:

  • Early onset of menstruation (before age 12)

  • Late onset of menopause (after age 55)

  • Obesity

  • Hormone replacement therapy

  • Alcohol consumption


Approximately 60% to 70% of all breast cancers are estrogen receptor (ER)-positive, meaning the cancer cells have estrogen receptors and depend on estrogen for growth. For those with ER-positive breast cancer, standard treatment involves blocking estrogen’s effects or reducing estrogen levels. 


Progesterone and Breast Cancer

Progesterone is another hormone that controls breast development and growth. Excessive exposure to progesterone over time may also contribute to breast cancer risk.


Research shows that progesterone receptors (PR) are present in about 60% of breast cancers. Of the different hormone receptor statuses, breast cancer that is both ER-positive and PR-positive tends to have a more favorable prognosis and more successful treatment outcomes.


However, some breast cancers are ER-positive and PR-negative. These cancers tend to be more aggressive and have lower survival rates than ER/PR double-positive breast cancers.


ER/PR Negative, Triple-Negative, and Triple-Positive Breast Cancer

Hormone receptor-negative breast cancer cells lack receptors for estrogen (ER) and progesterone (PR), meaning these cancer cells do not increase in response to hormonal influences. Approximately 25-30% of all breast cancer cases are represented by this type of breast cancer.


In triple-positive breast cancer, the proliferation of tumor cells is primarily influenced by the presence of estrogen receptors, progesterone receptors, and the human epidermal growth factor receptor 2 (HER2), a protein commonly found in breast cells.


Triple-negative breast cancer (TNBC) cells are characterized by the absence of estrogen and progesterone receptors and do not overexpress the HER2 protein. This type of cancer is more prevalent in women under 40 years old, particularly among Black women or those with a mutation in the BRCA1 gene.


Testosterone, Androgens, and Breast Cancer

Both men and women produce testosterone and other androgens. In men, androgens are responsible for male sex characteristics. However, higher levels of circulating androgens originating from the adrenal glands are linked to increased breast cancer risk in postmenopausal women.


Testosterone and other androgens may directly stimulate breast cell growth or get converted in fat tissue to estrogen, which can then spur cancer development and progression. Obesity is a risk factor for breast cancer and is associated with higher androgen levels.


While much more research is still needed, targeting androgen activity is an emerging area of interest for specific breast cancer treatments.


Hormone Therapy and Breast Cancer Treatment

Hormone therapies, like tamoxifen and aromatase inhibitors, are designed to block the effects of hormones or reduce their levels in the body. They are especially beneficial for hormone receptor-positive breast cancers.


  • Tamoxifen: Blocks estrogen’s effect on breast cancer cells.


  • Aromatase Inhibitors: Lower the amount of estrogen produced in postmenopausal women.


  • Ovarian Suppression: Premenopausal women might receive treatments to stop the ovaries from producing estrogen.


Although they are considered effective, hormone therapies can have side effects. Discuss potential risks and benefits with your healthcare professional.


Count On Us for Information, Resources, and Support 

Estrogen, progesterone, testosterone, and other hormones play significant and complex roles in the origins and behavior of breast cancer. Understanding these relationships has led to improved risk assessment, screening, prevention, and treatment approaches that consider hormone receptor status and other factors. Continued research on hormone-related mechanisms will help further advance breast cancer care and outcomes.


Whether you’re newly diagnosed with breast cancer, are navigating survivorship, or are the loved one of someone experiencing breast cancer, you can count on SurvivingBreastCancer.org to keep you informed. We provide educational information to help you better understand symptoms, testing, treatment options, surgery, etc., and podcasts that feature professionals, advocates, and caregivers who share valuable information.


Your donations enable SurvivingBreastCancer.org to offer resources and support every day, every month, and every year. 


Note: This article is designed to provide general information and not replace professional medical advice. Always discuss your options with your healthcare provider.



Learn more:









On the Podcast: Breast Cancer Conversations


Triple Positive Breast Cancer Under 30





SurvivingBreastCancer.org Resources & Support:



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