What is anastrozole?
Anastrozole is an aromatase inhibitor medication that reduces estradiol conversion in men undergoing testosterone replacement therapy to prevent estrogen-related side effects.
Anastrozole belongs to a class of drugs called aromatase inhibitors (AIs). In the context of testosterone replacement therapy, it works by blocking the enzyme aromatase, which converts testosterone into estradiol (the primary form of estrogen). Men on TRT can experience elevated estradiol levels as a side effect of increased testosterone, leading to gynecomastia, water retention, mood changes, and sexual dysfunction. Anastrozole prevents this conversion and keeps estradiol within a target range.
Dosing typically ranges from 0.25 mg to 1 mg per day, though many hormone therapy providers start with lower doses and adjust based on estradiol bloodwork. The goal is not to eliminate estradiol entirely but to maintain it at physiologic levels, usually between 20 and 30 pg/mL. Overuse of anastrozole carries real risks: excessive suppression of estradiol can cause joint pain, reduced bone density, lipid dysfunction, and erectile difficulties. Some men also report mood changes and fatigue when estradiol dips too low.
Response to anastrozole varies significantly between individuals due to differences in body composition, genetics, and aromatase enzyme expression. Regular monitoring through bloodwork is essential to find the right balance. A TRT clinic should not prescribe anastrozole as a one-size-fits-all adjunct but should tailor dosing to each patient's estradiol levels and tolerance.