Hormone Therapy

Hormone therapy is a type of systemic therapy – one that goes throughout the body. It is used to treat breast cancers that are hormone receptor-positive (HR+). HR+ breast cancers have receptors on the surface of their cells which bind to hormones in the body like estrogen and progesterone. Within the categorization of hormone positive breast cancer, breast cancers may be further classified as estrogen receptor-positive (ER+) or progesterone receptor-positive (PR+). When these hormones connect to the receptors on cancer cells, it can fuel the growth of the breast cancer, causing it to grow and spread faster.1

Hormone therapy may be used in various scenarios, such as a preventive medication in women at high risk of developing breast cancer, as an adjuvant (additional) treatment after surgery to reduce the risk of breast cancer recurring, or as a treatment in cases where breast cancer has recurred after initial treatment or when breast cancer has spread to other parts of the body (metastatic breast cancer).1

Types of hormone therapy

There are several different types of hormone therapy, including2:

  • Medications that block the estrogen receptors, anti-estrogens
  • Medications that help prevent the body from producing estrogen, aromatase inhibitors, gonadotropin releasing hormone agonists, and LHRH agonists
  • Surgery to remove the ovaries (oophorectomy) to stop the major estrogen source in the body


Anti-estrogens, or estrogen receptor antagonists, block the estrogen receptors. The medication binds to the estrogen receptor on the cell, which prevents the hormone from connecting. By blocking the hormone, these medications can slow or stop the breast cancer’s growth. Anti-estrogens used in the treatment of breast cancer include2:

Aromatase inhibitors

In women who are postmenopausal (their periods have stopped), estrogens in the body are no longer created by the ovaries but are created when androgens from the adrenal glands are converted to estrogen by the enzyme aromatase. Aromatase inhibitors block this enzyme from making estrogen, lowering the levels of estrogen in the body. This removes the fuel that HR+ breast cancers need to grow. Aromatase inhibitors used in the treatment of breast cancer include2:

Gonadotropin releasing hormone agonist

Gonadotropin is a hormone released by the pituitary gland that stimulates the ovaries to produce estrogen. By interrupting this hormone process, the patient’s body produces less estrogen. The lack of estrogen interferes with the cancer cell’s growth. A gonadotropin-releasing hormone agonist used to treat certain cases of breast cancer is Zoladex® (goserelin).3,4

Luteinizing hormone-releasing hormone (LHRH) agonist

The pituitary gland secretes the luteinizing hormone, which stimulates the production of estrogen by the ovaries. LHRH agonists work by suppressing the luteinizing hormone from being released by the pituitary gland, and this action reduces the amount of estrogen in the body, which in turn suppresses the growth of the breast cancer cells. An LHRH agonist used to treat certain cases of breast cancer is Lupron Depot® (leuprolide acetate).5

Common side effects of hormone therapy

Each medication is unique, and not everyone on a particular treatment experiences the same side effects. Common side effects of certain hormone therapies include2:

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Written by: Editorial Team | Last reviewed: March 2021.