What you should know about Aromatase Inhibitors

January 08, 2020

What you should know about Aromatase Inhibitors

What you should know about Aromatase Inhibitors


Aromatase inhibitors are a class of drugs used to stop the production of estrogen in postmenopausal women with estrogen receptor-positive breast cancer. This type of breast cancer uses the female sex hormone estrogen to grow the cancer cells. Hormone therapy, using aromatase inhibitors, is one of the most adjuvant therapies used to treat breast cancer after chemotherapy, radiation, and surgery.


Aromatase inhibitors reduce estrogen levels in the body, and in the process, prevent the stimulation of hormone-sensitive cancer cells. According to the Institute for Cancer Research (ICR) in the United Kingdom, aromatase inhibitors reduced the occurrence of death by 40% for breast cancer survivors in nine clinical trials. But for some, using aromatase inhibitors cause painful side effects, and people wonder if aromatase inhibitors really work and are worth it?


How they work


Aromatase inhibitors are used as adjuvant therapy. Adjuvant therapy is using medications to prevent the recurrence of breast cancer by blocking estrogen production. In premenopausal women, estrogen is primarily produced in the ovaries through the follicle-stimulating hormone (FSH) and to a lesser extent in the tissues of the breasts, liver, brain, skin, bone, and pancreas.

Postmenopausal women stop producing FSH, leaving the primary estrogen production to the peripheral tissues. Taking aromatase inhibitors block the process of aromatization in the cells that converts testosterone and aldosterone into estrogen through an enzyme called aromatase. The end result being that estrogen production may reduce by as much as 95% in postmenopausal women.


Who can take them


As mentioned, aromatase inhibitors are used to prevent the reoccurrence of postmenopausal breast cancer, but for those with metastatic breast cancer, treatment can be useful too. Metastatic breast cancer is when cancer cells have spread to other parts of the body, such as the brain or liver. 


Advanced breast cancers with spreading malignancy can benefit from aromatase inhibitors. For premenopausal women, aromatase inhibitors aren't effective because the substance that stimulates estrogen isn't aromatase but FSH. After menopause, FSH production stops.




The U.S. Food and Drug Administration has approved three aromatase inhibitors:


  • Arimidex
  • Femara
  • Aromasin


All three are taken in tablet form, once a day. Arimidex and Femara can be taken at any time, but Aromasin should be taken with food. Usually, breast cancer patients take aromatase inhibitors for five years or longer.


The side effects of aromatase inhibitors


While aromatase inhibitors can be effective in preventing breast cancer recurrence, the drugs can cause side effects. Since they lower estrogen levels, the most common side effects are menopausal symptoms, including:


  • Hot flashes
  • Vaginal dryness
  • Weight gain
  • Insomnia
  • Night Sweats

In addition to menopausal symptoms, the most common reported short-term side effect is joint and muscle pain. Other more serious complications can occur from women taking aromatase inhibitors for an extended period, such as bone loss, leading to osteoporosis. There's also an increased risk of heart disease and diabetes.


While aromatase inhibitors are a viable method of breast cancer prevention and recurrence, the drugs can come with some short and long term side effects for women’s health.