Anastrozole (Arimidex) is a non-steroidal aromatase inhibitor originally developed for hormone-positive breast cancer.
Mechanism — Reversibly inhibits aromatase, the enzyme converting androgens to estrogens. Reduces estradiol production from testosterone, DHEA, and androstenedione.
Use case — Off-label on TRT when estradiol elevation produces symptoms (water retention, nipple sensitivity, mood). Typical 0.25-0.5 mg 1-2x/week. Crushing estrogen entirely is a mistake — men need E2.
Caveats — Over-suppression causes joint pain, dry skin, lipid worsening, libido crash, and bone density loss. The right approach on TRT is usually managing dose and frequency before adding an AI. Get an E2 sensitive assay (LC-MS/MS) before deciding.