What anastrozole does
Anastrozole inhibits aromatase, the enzyme that converts testosterone to estradiol. On TRT, more testosterone = more substrate for aromatization = more estradiol. In some men this raises E2 above optimal. Anastrozole blunts the conversion, lowering E2.
Why it's overused
Historical TRT culture treated estradiol as an enemy, assumed lower is always better. Many TRT clinics still prescribe anastrozole prophylactically with every TRT script. The result: many men have iatrogenic crashed estradiol with the symptoms (joint pain, low libido, depressed mood) it causes.
When anastrozole is appropriate
- Sensitive estradiol confirmed >45 pg/mL by LC-MS/MS assay
- WITH symptoms: water retention, breast tenderness, mood lability, gynecomastia risk
- After addressing upstream drivers (visceral fat, alcohol, dose) hasn't resolved
- In genetic high-aromatizers
- Some men with significant visceral fat during weight loss phase
When anastrozole is not appropriate
- Prophylactically, before any testing
- Based on standard E2 immunoassay only (unreliable in men)
- For E2 in 30-40 range without symptoms
- For E2 elevation that hasn't been confirmed by repeat testing
- When upstream drivers (visceral fat, alcohol, excessive TRT dose) haven't been addressed
- In men already showing signs of low E2 (joint pain, low libido)
Dosing
When used, doses are small:
- 0.25 mg once weekly, most common starting point
- 0.5 mg once weekly, moderate
- 0.5 mg twice weekly, only for confirmed high aromatizers
- 1 mg multiple times per week, rarely appropriate
Re-test sensitive E2 at 4-6 weeks. Adjust based on results, not assumed effect.
Address upstream first
Before adding anastrozole, address the drivers of elevated E2:
- Reduce TRT dose if total T is supraphysiologic
- Address visceral fat (more fat = more aromatization)
- Reduce alcohol (impairs liver E2 clearance)
- Improve sleep (cortisol-related disruption)
Many "high E2" patterns resolve without anastrozole when these are addressed.
The clinical pearl: The reflex "every TRT patient needs anastrozole" approach harms more men than it helps. Use it when confirmed-high E2 plus symptoms exist; otherwise leave it alone.
Bottom line
Anastrozole is a useful tool for the right patient, but it's frequently misused as a default add-on. Modern TRT prescribes it only when sensitive estradiol confirms elevation and symptoms are present. The reflex prescription has caused more iatrogenic harm than benefit in male hormone optimization.