Medical Definition of Aromatase inhibitor

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Last Editorial Review: 1/24/2017

Aromatase inhibitor: A drug that inhibits the enzyme aromatase and by that means lowers the level of the estrogen estradiol. Aromatase inhibitors represent a class of antiestrogens.

Aromatase catalyzes the conversion of testosterone (an androgen) to estradiol (an estrogen) in many tissues including the adrenal glands, ovaries, placenta, testicles, adipose (fat) tissue, and brain. Estrogen is produced directly by the ovaries and is also made by the body using aromatase. Aromatase inhibitors cannot do anything about estrogen produced by the ovaries, but they do interfere with the body's use of aromatase.

The growth of many breast cancers is promoted by estrogens. Most estrogen after menopause comes from the action of aromatase. Aromatase inhibitors may therefore be used to treat estrogen-dependent tumors after the menopause. Aromatase inhibitors are used mostly in women who have reached menopause, when the ovaries are no longer producing estrogen.

The aromatase inhibitors approved by the US Food and Drug Administration include anastrazole (Arimidex), exemestane (Aromasin), and letrozole (Femara).

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Last Editorial Review: 1/24/2017