Oestradiol (spelled estradiol in American English, and often written as E2) is usually thought of as a female hormone, but men make and use it throughout life. In men, most of it comes from testosterone converted by an enzyme called aromatase, which is found in fat tissue, the brain, bone and the testes.
Levels in men are far lower than in premenopausal women, but they are not trivial, and the body relies on them. Oestradiol also feeds back to the brain to help regulate LH and so testosterone production, and it raises SHBG, the protein that binds testosterone in the blood.3
The online idea that men should keep oestrogen as low as possible does not match the research. Too much can cause problems, but too little causes problems of its own.
What does oestradiol do in men?
In a landmark trial, oestrogen deficiency was mainly responsible for gains in body fat when men's sex hormones were lowered, and both oestrogen and testosterone deficiency contributed to worse sexual function.1
The study, published in 2013, gave 400 healthy men aged 20 to 50 a drug to switch off their own hormone production, then added back different doses of testosterone gel. Half also took anastrozole, a drug that blocks the conversion of testosterone to oestradiol.1 That design let the researchers separate the effects of the two hormones.
Loss of lean mass, muscle size and strength tracked with testosterone. Rising body fat tracked mainly with oestradiol. Sexual desire and function fell as both dropped.1 In plain terms, part of what men attribute to testosterone is actually being done by the oestradiol made from it.
Is high oestradiol in men a problem?
It can be, but it is less common than the internet suggests, and many so-called high readings come from unreliable tests. When levels are genuinely high, breast tenderness or swelling is the classic sign doctors look for.
Oestradiol tends to run higher in men carrying more body fat, because fat tissue contains aromatase, and it rises when testosterone is given as treatment because there is more raw material to convert. Advanced liver disease and heavy alcohol use are also linked with higher oestrogen.3 Unexplained breast changes are worth seeing a GP about promptly. A genuinely high level in a man who is not on any hormone treatment is unusual enough to be investigated for a cause rather than simply blocked.
How is oestradiol measured in men?
Accurately, only with a sensitive method. In more than 3,000 European men, standard platform immunoassays agreed poorly with mass spectrometry for oestradiol and caught only 13% of genuinely low values.2
The same study found the immunoassay did reasonably well at spotting high oestradiol, but the authors concluded it may only be suitable for that purpose in men.2 If your oestradiol result is being used to make a treatment decision, it is reasonable to ask whether the lab used a sensitive or mass spectrometry-based assay.
Should men block oestrogen?
Not as a routine, and never without medical supervision. The 2013 trial showed that blocking conversion to oestradiol led to more body fat and contributed to poorer sexual function, even when testosterone was replaced.1
Some men on testosterone therapy are told to add an oestrogen blocker to keep their numbers low. That decision belongs with a doctor who can see the full picture, not a forum. If you have symptoms you think are hormonal, talk to a doctor about proper testing first. For how hormones interact with desire, see does testosterone affect sex drive?
Common questions
Do men need oestrogen?
Yes. Research that lowered men's hormones under controlled conditions found oestradiol deficiency drove increases in body fat and contributed to reduced sexual desire and function.1
What causes high oestradiol in men?
Common reasons include excess body fat, testosterone treatment, heavy drinking and liver disease.3 A single high reading on a standard test should be confirmed before anyone acts on it.
Is estradiol the same as oestradiol?
Yes. Oestradiol is the British spelling and estradiol the American one. Lab reports may use either, and some simply write E2.
Read more on this
How testosterone changes after 40 (and what actually helps)
Does testosterone affect sex drive? Separating myth from mechanism
Sources
- Finkelstein JS, et al. Gonadal steroids and body composition, strength, and sexual function in men. N Engl J Med. 2013;369(11):1011-1022. PubMed
- Huhtaniemi IT, et al. Comparison of serum testosterone and estradiol measurements in 3174 European men using platform immunoassay and mass spectrometry; relevance for the diagnostics in aging men. Eur J Endocrinol. 2012;166(6):983-991. PubMed
- Goldman AL, et al. A reappraisal of testosterone's binding in circulation: physiological and clinical implications. Endocr Rev. 2017;38(4):302-324. PubMed
Not medical advice. Written by Eric Stephens from the research cited above; not reviewed by a doctor. If something worries you, see a GP.