Anastrozole
Also known as: Arimidex, AI (aromatase inhibitor)
An aromatase inhibitor used off-label to control estrogen elevation on testosterone therapy. Prescription medication (approved for breast cancer).
Last updated
Mechanism of Action
Anastrozole reversibly inhibits the aromatase enzyme, which converts testosterone to estradiol. On TRT this lowers estradiol when it rises above the desired range. Because some estradiol is essential for male bone, lipid, libido, and mood health, over-suppression is harmful — dosing is conservative and lab-guided.
- Half-life
- ~46 hours
- Administration Routes
- Oral
- Research Status
- Clinical
Reported Benefits
- Lowers elevated estradiol on testosterone therapy
- Can reduce estrogenic water retention and gynecomastia risk
Potential Side Effects
- Over-suppression of estradiol (joint pain, low libido, mood changes)
- Reduced bone mineral density with excessive use
- Adverse lipid changes
Common Dosing
When used, protocols report small doses (a fraction of a milligram) once or twice weekly, titrated to estradiol labs. Many men on well-managed TRT need no aromatase inhibitor. Physician-directed only.
The dosing information above is aggregated from research literature and anecdotal community reports for educational purposes only. It is not a recommendation, prescription, or medical advice. Peptides are sold as research chemicals only and are not intended for human use.
Contraindications
- Women who are or may become pregnant
- Osteoporosis / low bone density (relative)
- Do not use to drive estradiol below the healthy male range
Testosterone Cypionate
A long-acting injectable testosterone ester used clinically for testosterone replacement therapy (TRT) in men with diagnosed hypogonadism. Prescription medication.
Testosterone Enanthate
A long-acting injectable testosterone ester used for testosterone replacement therapy. Clinically near-interchangeable with cypionate. Prescription medication.
HCG (Human Chorionic Gonadotropin)
A glycoprotein hormone produced in pregnancy that mimics luteinizing hormone, used clinically to stimulate gonadal function. It is studied to support testosterone production and fertility.
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Effects of aromatase inhibition in elderly men with low or borderline-low serum testosterone levels
2004
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Effects of aromatase inhibition on bone mineral density and bone turnover in older men with low testosterone levels
2009
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A Randomized Prospective Double-Blind Comparison Trial of Clomiphene Citrate and Anastrozole in Raising Testosterone in Hypogonadal Infertile Men
2015
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Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 years' adjuvant treatment for breast cancer
2005