Estrogen-synthesis inhibitors

Aromatase inhibitors that inhibit the androgen aromatization in estrogens and thus block estrogen synthesis. 

Anastrozole, a selective nonsteroidal inhibitor of aromatase (the enzyme required for estrogen synthesis. Figures 40-2 and 40-5), is effective in some women whose breast tumors have become resistant to tamoxifen (see Chapter 54). Letrozole is similar. Exemestane, a steroid molecule, is an irreversible inhibitor of aromatase. Like anastrozole and letrozole, it is approved for use in women with advanced breast cancer (see Chapter 54). 

The prototypical steroidal inhibitor of aromatase (the enzyme required for estrogen synthesis) is testolactone. It is a weak inhibitor of the enzyme, and large quantities need to be administered to achieve clinical effect. 

Letrozole and anastrozole are called aromatase inhibitors because they block the activity of the aromatase enzyme, which is responsible for estrogen synthesis. This inhibits tumor growth in those forms of breast cancer that are stimulated by estrogen. 

Mode of action aromatase inhibitor —>1 estrogen synthesis... 

E. Estrogen and Progesterone Agonists, Antagonists, and Synthesis Inhibitors ... 

Aromatase inhibitors serve to eliminate ex-traovarian synthesis of estrogens in breast cancer patients. This can be achieved effectively only in postmenopause because, as an FSH-dependent enzyme, ovarian aromatase is subject to feedback regulation of female Luellmann, Color Atlas of Pharmacology 2005 Thieme All rights reserved. Usage subject to terms and conditions of license. 

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