A Comprehensive Guide to Aromatase Inhibitors : Clinical Uses Unveiled

Aromatase inhibitors are a class of drugs that stop the production of estrogen in women who are post-menopausal and are used mainly for treating hormone receptor-positive breast cancer.

More about aromatase inhibitase and their most common clinical use are discussed below.

Aromatase inhibitors (AIs), used in hormone therapy or endocrine therapy, are used in treating breast cancer in postmenopausal women and gynecomastia in men.^{(1, 2)} Aromatase inhibitors lower the levels of estrogen by restricting an enzyme in fat tissue (aromatase) from changing other hormones into estrogen.

Aromatase inhibitors do not stop the ovaries from making estrogen, rather they simply lower the levels of estrogen in women whose ovaries are not making estrogen (especially in cases of menopausal women).

Anastrozole (Arimidex), Exemestane (Aromasin), and Letrozole (Femara) are the aromatase inhibitors that have been shown in studies to reduce the risk of lower breast cancer. These drugs are generally taken for five years once a day to reduce the risk of breast cancer.

Aromatase inhibitors work by inhibiting the action of aromatase enzyme, which converts androgen hormones into estrogens by aromatization. Breast cancer cells are fueled by estrogen. Thus decreasing the production of estrogen suppresses the recurrence of the breast tumor tissues.

The ovaries in premenopausal women are the main source of estrogen, while in the case of post-menopausal women, most of the estrogen in their bodies is produced in peripheral tissues (outside the CNS), and also a few CNS sites in multiple regions within the brain.

In premenopausal women, most of the estrogen is produced in the ovaries. However, in postmenopausal women, estrogen is primarily produced in their bodies’ peripheral tissues. Because certain breast cancers respond to estrogen, reducing the production of estrogen at the site of the cancer (i.e. the adipose tissue of the breast) with aromatase inhibitors has proved to be an effective treatment for hormone-sensitive breast cancer in most postmenopausal women.⁽³⁾

Breast cancers in premenopausal women are usually not treated with aromatase inhibitors, because before menopause, the reduction in estrogen hormone activates the hypothalamus and pituitary axis to increase secretion of gonadotropin, which can ultimately stimulate the ovary to increase the production of androgen.

In large studies, both exemestane and anastrozole drugs have been shown to lower the risk of breast cancer in postmenopausal women who are at increased risk. Although some expert groups include these drugs as options for reducing breast cancer risk in post-menopausal women, they are not being approved by the FDA to lower the risk of breast cancer.

Aromatase inhibitor Letrozole has been proposed for ovarian stimulation to treat unexplained female infertility. The National Institute of Child Health and Development has funded a multi-center study that mentioned that ovarian stimulation using aromatase inhibitor letrozole could result in a significantly lower frequency of multiple gestation (i.e. twins or triplets).⁽⁴⁾

One more use of aromatase inhibitors is that it has been an approved treatment approach for gynecomastia in children and adolescents.⁽⁵⁾ Gynecomastia is a condition of overdevelopment of breast tissues in boys or men.

Aromatase inhibitors can cause certain common side effects, such as night sweats, hot flashes, and vaginal dryness. Additionally, these drugs can also result in muscle and joint pain.

Sometimes, aromatase inhibitors can cause serious side effects like bone loss or bone thinning (osteoporosis), broken bones, and heart problems. These drugs can also raise cholesterol level. Women with pre-existing heart disease should not use aromatase inhibitors.

Aromatase inhibitors or the drugs that stop estrogen production in postmenopausal women and are primarily used for treating breast cancers. They are also approved for treating gynecomastia. These drugs might cause mild to severe side effects including hot flashes, vaginal dryness, osteoporosis, and heart problems. If you are taking aromatase inhibitors and experiencing side effects due to the drug, tell your doctor immediately.

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