For Peak Performance on Testosterone, Should I Block Aromatase and Keep Estradiol Low?
Quick Answer
No, and the best trial we have on this question shows the opposite. In a randomized, placebo-controlled study, men who had aromatization blocked while on testosterone gained no more muscle or strength than men at the same testosterone dose with estradiol left intact. What blocking it did produce was more body fat, including visceral fat, and worse sexual desire and erectile function, at the identical testosterone dose.
Muscle and strength tracked with testosterone level. Fat and sexual function tracked with estradiol. Crashing estradiol didn't help either goal, and it actively worked against two of them.
Where This Advice Comes From
The logic isn't crazy on its face. More than 80% of the estradiol circulating in men comes from peripheral conversion of testosterone by the aromatase enzyme, not from direct production. So more testosterone does mean more substrate available for conversion, and in men running non-medical, supraphysiologic doses of anabolic steroids, that conversion can genuinely run high enough to cause real problems, water retention, gynecomastia, mood swings. An aromatase inhibitor has a legitimate place in that specific scenario.
The advice you heard takes that narrow, symptom-driven use case and generalizes it into a blanket rule: more testosterone means you should preemptively suppress estrogen, regardless of dose, regardless of symptoms, regardless of what it's actually optimizing for. That generalization is where it stops matching the evidence, especially for men on physiologic-range testosterone therapy rather than bodybuilding-level dosing.
What the Trial Actually Found
The relevant study is a 2013 randomized trial published in the New England Journal of Medicine. Researchers took 400 healthy men aged 20 to 50, suppressed their own testosterone and estradiol production with a GnRH agonist, then randomly assigned them to one of five testosterone gel doses for 16 weeks. Half of the men also received anastrozole to block conversion of that testosterone to estradiol, while the other half had normal aromatization. Because testosterone dose was fixed and identical between the two groups at each level, any difference between them isolates what estradiol itself was doing.
Body fat. At every matched testosterone dose, blocking aromatization significantly increased percentage body fat, subcutaneous fat area, and intraabdominal (visceral) fat area compared with men whose estradiol was allowed to rise normally. Fat accumulation tracked with estradiol suppression, not with testosterone dose.
Lean mass and strength. Total lean mass, thigh muscle area, and leg-press strength depended on testosterone dose. Blocking aromatization added nothing here. Men on anastrozole gained the same muscle and the same strength as men at the identical testosterone dose who kept normal estradiol production.
Sexual function. This is where suppressing estradiol actively backfired. Compared with men on the same testosterone dose with intact aromatization, the men whose estradiol was blocked had significantly worse sexual desire and worse erectile function.
Put together: no muscle or strength advantage from blocking estradiol, and a clear cost in fat mass and sexual function at every dose tested. If performance means body composition and sexual function, which is usually what people mean by it, this specific intervention worked against both.
The Testosterone-to-Estradiol Ratio Isn't Something to Chase Toward Zero
The useful clinical tool here is the ratio between testosterone and estradiol, not a fixed low target for estradiol on its own. That ratio has a floor and a ceiling, and problems show up at both ends, not just from estrogen running too high. Men who deliberately push their estradiol down toward the bottom of the detectable range are pushing past the upper edge of that ratio, into territory associated with joint pain, brain fog, poor sleep, and reduced libido, the same symptom cluster people associate with being undertreated on testosterone in the first place. There isn't a performance zone that opens up below normal estradiol levels. There's just estrogen deficiency with a testosterone number attached to it.
If someone recommends adding an aromatase inhibitor to a testosterone protocol purely as a preventive measure, with no symptoms of estrogen excess and no lab work showing an unfavorable testosterone-to-estradiol ratio, that recommendation isn't supported by the trial data above. It's treating a problem that, for most men on physiologic-range therapy, isn't present.
When an Aromatase Inhibitor Does Make Sense
There's a real, narrower use case: confirmed symptoms of estrogen excess, nipple tenderness, early glandular changes, significant water retention, paired with labs showing a testosterone-to-estradiol ratio that's actually out of range. That's a symptom-and-lab-driven decision made with a physician, not a default addition to a testosterone protocol and not a strategy for improving performance. I've written a longer piece specifically on anastrozole in men on TRT that walks through that distinction in more detail if you want to go deeper on it.
If you're currently on testosterone therapy and someone has recommended adding an aromatase inhibitor, or you're already on one and not sure why, that's worth reviewing against your actual labs and symptoms rather than a general rule of thumb. If you'd like an in-clinic consultation, here are all of the practices I see patients in. Prefer to start with a question first? Reach out directly by email or Instagram.
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References
- Finkelstein JS, Lee H, Burnett-Bowie SA, et al. Gonadal steroids and body composition, strength, and sexual function in men. N Engl J Med. 2013;369(11):1011–1022. PMID: 24024838. doi: 10.1056/NEJMoa1206168.
- Longcope C, Kato T, Horton R. Conversion of blood androgens to estrogens in normal adult men and women. J Clin Invest. 1969;48(12):2191–2201.
- Khosla S, Melton LJ 3rd, Riggs BL. Clinical review 144: estrogen and the male skeleton. J Clin Endocrinol Metab. 2002;87(4):1443–1450. PMID: 11932262.
- Swislocki AL, Eisenberg ML. A review on testosterone: estradiol ratio—does it matter, how do you measure it, and can you optimize it? World J Mens Health. 2025;43(3):453–464. doi: 10.5534/wjmh.240029.
This content is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Anastrozole and other aromatase inhibitors are prescription medications; their use in men on testosterone therapy is off-label and should be based on individual symptoms and laboratory values under physician supervision, not added routinely or as a performance strategy. Individual clinical decisions should be made in consultation with a licensed physician who has reviewed your complete medical history and current laboratory values. Do not start, stop, or adjust any medication without guidance from your treating provider. Dr. Wilcox is licensed to practice in multiple states. See About for current licensure.