Estrogen in men’s bodies is converted from testosterone. So a high testosterone level can mean high estrogen levels in absolute terms. But high estrogen as a ratio of testosterone can result in a low total testosterone level. This can further worsen the ratio of testosterone to estrogen, eventually resulting in higher body fat.
Since body fat is where aromatase is stored and aromatase is the the enzyme that converts testosterone to estrogen, it’s often presumed that high body fat causes low testosterone due to high estrogen. That often is the case. Thus, ‘lower estrogen to raise testosterone’ is the oft-repeated prescription.
But this can be a mistake. Low middle-aged testosterone isn’t always the result of high body fat. Futhermore, when it is the result of high body fat, it might not be due to high estrogen.
Men treating their low testosterone as an estrogen problem when it’s not can wreak havoc on other bodily functions. Specifically, it can send a guy’s libido right into the dumpster.
When High Estrogen causes Low Testosterone
The theory that high estrogen leads to low testosterone in men is based on the loop feedback nature of endogenous testosterone production. The brain’s hypothalamus monitors blood levels of the male hormone. When levels drop, it sends gonadotropin releasing hormone (GnRH) as a signal to the pituitary gland activating release of luteinizing hormone (LH). When LH reaches the leydig cells in the testes, they are triggered into testosterone production. 
Estrogen competes with testosterone for hormone receptor sites. When high levels of the female hormone fill too many cell’s receptor sites, a ‘false signal’ is picked up by the hypothalamus. It essentially reads the high estrogen as adequate testosterone, thus producing a weak signal for any further testosterone production.
This theory of the cause of hypogonadism in men is certainly supported by tests with the drug clomifene. A non-steroidal selective estrogen receptor modulator (SERM), clomifene (or ‘clomid’) has been shown in at least one study to nearly double the testosterone levels of hypogonadal men. It only took a daily dose of 25 mg. of this anti-estrogen, for 3 – 6 months, to produce this effect.
That study was done on 125 male participants who complained of low libido symptoms. They started with average ‘T-levels’ of 300 – 400 nanograms per decilitre. They finished with T-levels of 600 – 750 nanograms per decilitre. The ‘lower estrogen to raise testosterone’ formula certainly worked for them.
What’s not reported is whether this change had a positive effect on libido.
Bodyfat and Testosterone: Another Theory
It’s possible that high body fat lowers testosterone via a mechanism other than estrogen.
A study of 50 male teenagers, half of whom were overweight, is revealing. The overweight teens had a bodyweight index (BMI) of 36 – the slender ones a BMI of 20. The overweight teens (aged 14 – 20) averaged half the testosterone of the slender group.
The first culprit of suspicion among the researchers was estradiol (male estrogen). However, the chubby youngster’s estrogen levels did not correlate with their reduced ‘T’; they only had slightly raised estrogen.
What did the researchers find that did correlate?
Lowered insulin sensitivity.
They measured this with HOMA-IR (fasted glucose multiplied by insulin level). They found that the higher the HOMA-IR, the lower the free testosterone of the subjects.
The researchers advanced their own theory for this based on gonadotropin releasing hormone (GnRH). Again, this is the signaling hormone from the hypothalamus to the pituitary to send a signal for more T-production. GnRH is usually released when insulin levels rise. But when insulin sensitivity is reduced, GnRH stops releasing in response to insulin spikes.
When Estrogen is Not the Cause of ‘Low T’
The problem with eradicating estrogen is that it can (among other things) snuff out sex drive.
Since estradiol is derived from testosterone, we’re unlikely to have sufficient estrogen while producing low testosterone. In fact, one of the major reasons for low testosterone causing low libido and reduced sexual function is that it results in low estrogen.
That’s why I’m curious about the more ‘subjective’ outcomes of that clomifene study mentioned above. Only a post-treatment survey of sexual performance and desire can determine if libido was affected (positively or negatively) by the use of clomifene.
Why would too much drop in estrogen ruin sex drive?
A 2013 study revealed that reducing men’s testosterone and estrogen took a bigger toll on their libido and sexual function than reducing testosterone by itself.
This is good reason to be careful with supplements such as curcumin, resveratrol, and diidolylméthane (DIM). These can possibly raise testosterone by lowering estrogen. But I’ve seen some online anecdotal feedback on each of these respective ‘T-boosters’ claiming their use sent user’s sexual desires down into the realm of the nearly imperceptible. That’s a really lousy pitfall, even if the upshot were higher testosterone.
To find out if your libido is being negatively affected by estrogen (too high or too low), it’s best to just get blood levels checked along with testosterone. The ideal estradiol level for men is between 21.80 and 30.11 pg/mL.
References
Carlos Teodósio Da Ros, Márcio Augusto Averbeck. ‘Twenty-five milligrams of clomiphene citrate presents positive effect on treatment of male testosterone deficiency – a prospective study’ Brazilian Journal of Urology (vol.38, no.4) July-Aug. 2012
Muniza Mogri, Sandeep Dhindsa, Teresa Quattrin, Husam Ghanim, Paresh Dandona. ‘Testosterone concentrations in young pubertal and post-pubertal obese males.’ Clinical Endocrinology (Volume 78, Issue 4, Pages 593–599) April 2013
Joel S. Finkelstein, M.D., Hang Lee, Ph.D., Sherri-Ann M. Burnett-Bowie, M.D., M.P.H., J. Carl Pallais, M.D., M.P.H., Elaine W. Yu, M.D., Lawrence F. Borges, M.D., Brent F. Jones, M.D., Christopher V. Barry, M.P.H., Kendra E. Wulczyn, B.A., Bijoy J. Thomas, M.D., and Benjamin Z. Leder, M.D. ‘Gonadal Steroids and Body Composition, Strength, and Sexual Function in Men’ The New England Journal of Medicine (2013; 369:1011-1022) Sept. 2013
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