Increasing testosterone by inhibiting aromatase

Kindke has an interesting post on an easy way to increase testosterone, through inhibiting the enzyme aromatase. This enzyme is responsible for converting testosterone (T) into estradiol. In the study Kindke linked, T increased as much as 60% in healthy young men with normal T levels. That’s pretty good. See charts below.

I looked for some other studies. Just so we can see whether the same effects hold in older men with low T, look at this one: Effects of Aromatase Inhibition in Elderly Men with Low or Borderline-Low Serum Testosterone Levels.

As men age, serum testosterone levels decrease, a factor that may contribute to some aspects of age-related physiological deterioration. Although androgen replacement has been shown to have beneficial effects in frankly hypogonadal men, its use in elderly men with borderline hypogonadism is controversial. Furthermore, current testosterone replacement methods have important limitations.

We investigated the ability of the orally administered aromatase inhibitor, anastrozole, to increase endogenous testosterone production in 37 elderly men (aged 62–74 yr) with screening serum testosterone levels less than 350 ng/dl. Subjects were randomized in a double-blind fashion to the following 12-wk oral regimens: group 1: anastrozole 1 mg daily (n = 12); group 2: anastrozole 1 mg twice weekly (n = 11); and group 3: placebo daily (n = 14). Hormone levels, quality of life (MOS Short-Form Health Survey), sexual function (International Index of Erectile Function), benign prostate hyperplasia severity (American Urological Association Symptom Index Score), prostate-specific antigen, and measures of safety were compared among groups.

Mean ± SD bioavailable testosterone increased from 99 ± 31 to 207 ± 65 ng/dl in group 1 and from 115 ± 37 to 178 ± 55 ng/dl in group 2 (P < 0.001 vs. placebo for both groups and P = 0.054 group 1 vs. group 2). Total testosterone levels increased from 343 ± 61 to 572 ± 139 ng/dl in group 1 and from 397 ± 106 to 520 ± 91 ng/dl in group 2 (P < 0.001 vs. placebo for both groups and P = 0.012 group 1 vs. group 2). Serum estradiol levels decreased from 26 ± 8 to 17 ± 6 pg/ml in group 1 and from 27 ± 8 to 17 ± 5 pg/ml in group 2 (P < 0.001 vs. placebo for both groups and P = NS group 1 vs. group 2). Serum LH levels increased from 5.1 ± 4.8 to 7.9 ± 6.5 U/liter and from 4.1 ± 1.6 to 7.2 ± 2.8 U/liter in groups 1 and 2, respectively (P = 0.007 group 1 vs. placebo, P = 0.003 group 2 vs. placebo, and P = NS group 1 vs. group 2). Scores for hematocrit, MOS Short-Form Health Survey, International Index of Erectile Function, and American Urological Association Symptom Index Score did not change. Serum prostate-specific antigen levels increased in group 2 only (1.7 ± 1.0 to 2.2 ± 1.5 ng/ml, P = 0.031, compared with placebo). These data demonstrate that aromatase inhibition increases serum bioavailable and total testosterone levels to the youthful normal range in older men with mild hypogonadism. Serum estradiol levels decrease modestly but remain within the normal male range. The physiological consequences of these changes remain to be determined.

The older men in this study had a huge increase in T, more than double the level of free T in one group. These are very worthwhile results, comparable (I believe) to actual T supplementation.

So, aromatase inhibitors work in both young, normal T level, and older, abnormal T level, men. Notable is that the aromatase inhibitor mentioned above, anastrozole, is now generic and fairly cheap. Don’t know if it can be had from overseas pharmacies.

Also, I posted the other day that resveratrol increases sperm counts and T levels in rats. The mechanism might very well be aromatase inhibition: The red wine polyphenol resveratrol displays bilevel inhibition on aromatase in breast cancer cells.

Don’t know what if any downside aromatase inhibitors have. It seems a whole lot easier to take them than to use injectable T or any other kind.


Leave a Comment:

Anonymous says November 18, 2013

“Don’t know if it can be had from overseas pharmacies.”

It can; just search for “Anastrozole online pharmacy”. $1/pill generic, $8 brand name.

Kindke says November 19, 2013

Taking AI’s is definitely easier than injecting T, probably safer aswell but tbh exogenous T alone is actually very safe especially at normal physiological levels. Even at supra-physiological levels I personally believe T is quite safe ( 300-500mg per week ). The major threat of exogenous androgens is “permanent” shutdown of the HPTA, however that is reported to be rare on T alone, unless the T is done for extended periods like years. Excess acne is a concern but not everyone breaks out.

The other concern is prostrate hypertrophy but I read another interesting paper which suggests it is estrogen causing this, not T, with the estrogen coming from excess aromatase activity, ( which I think is driven by excess insulin )

Overall aromatase inhibition is obviously not going to be as effective as exogenous T in raising T to very high levels or achieving an anabolic response, but it does have the advantage of not causing HPTA shutdown.

In the study on my blog I noticed aromasin took estrogen levels to the borderline low level of what is considered normal in men. Its something to be aware of when taking AI’s, you need to not overdose because low estrogen is unpleasant.

Mangan says November 19, 2013

Kindke, I noted in I think every aromatase study I read that the authors were careful to note that estradiol levels stayed within the normal male range, which as you note appears to be very important. The estrogens have important functions even in men, like maintaining bone mineral density. It seems more likely to have an abnormal estradiol (the most potent estrogen) when supplementing T rather than using an aromatase inhibitor. So perhaps I should have emphasized that as another advantage (at least that I see) of inhibiting aromatase over taking T.

    Dave Pinsen says August 23, 2014

    I asked my endrocrinologist about this last time I saw him. Short version: if you need supplementation to maintain normal testosterone levels long term, the solution is testosterone itself. AIs aren’t a long term solution because of the bone issue, according to him. There’s another drug (I forget the name of it) that endos sometimes prescribe short term if a) they think there’s a chance of jump starting production of T after an illness or something or b) temporarily in lieu of T replacement for men trying to have kids who are concerned about fertility effects.

    Fortunately, my T-levels were normal last time, so it seems like the lifting is sufficing to keep the T flowing for me for now.

    Mangan says August 24, 2014

    A doctor once told me that by the time you’re referred to an endocrinologist, you’re beyond help. No offense, but I think your endo is wrong. Even with AI, you adjust the dose so estradiol stays w/in normal range.

Anonymous says April 8, 2014

“this study also reported that cigarette smoke (obtained using methylene chloride and aqueous traps) and tobacco leaves (70% ethanol extract; Nicotiana tabacum L.) also potently inhibited aromatase, as reported in cigarette equivalents”

*Lights cigarette*
*Looks at camera*
“That’s why they call me the Marlboro Man not Manboob”

Anonymous says April 9, 2014

Anyone know if natural aromatase inhibitors like APE (or the herbs from which it’s made) work? Things like tongkat ali, etc.

The FDA is coming after testosterone - Rogue Health and Fitness says October 31, 2014

[…] would say that this gives extra impetus to the use of aromatase inhibitors, which I discussed both here and in my book. Aromatase inhibitors, such as anastrozole, can increase testosterone levels by 50 […]

My experience with an aromatase inhibitor - Rogue Health and Fitness says March 3, 2015

[…] own doctor shot back with a suggestion: an aromatase inhibitor. Aromatase inhibitors work to boost T by decreasing the production of estrogens, especially […]

Tuba says February 23, 2016

We are not “between the cracks” but in an area where there is not a good amount of information. There are several complications. Most men taking anastrozole are also taking T or some other steroid. That’s a complex chemical juggling act and dozens of sites about said. I don’t need “replacement” T but I wouldn’t might a little more to help in the gym. My E2 is 33.3. I’d like to lower it some but keep it out of the problem low end which is around 12. The way to get there is anastrozole. The headache is how much, how often. Also if you hit a level is maintenance a smaller dose than the dose to get it down? Or, does one just take smaller doses over a longer time, say .25mg a week? And is there a difference between 1mg a week vs two .50 mg a week. The half life is 46.8 hours. That nearly splits the week into two equal parts, or close enough. So, once a week? Twice a week? How much? And test how often. Those are all kind of foggy.

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