Men produce estrogen throughout their entire lives, and it plays a surprisingly important role in bone strength, brain function, heart health, and sexual desire. The primary form of estrogen in men is estradiol, and normal levels fall between 20 and 50 pg/mL. Rather than being a “female hormone” that men happen to have, estrogen is an active player in male physiology, and problems arise when levels swing too high or too low.
How Men Produce Estrogen
Men don’t produce estrogen the way women do. Instead, the body converts testosterone into estradiol through a process called aromatization, driven by an enzyme called aromatase. This conversion happens in fat tissue, the testes, brain, bone, liver, breast tissue, and blood vessels. Fat tissue is the dominant site. A weaker form of estrogen called estrone is also produced through this same enzyme system and can be further converted into estradiol.
This means estrogen levels in men are directly tied to two things: how much testosterone is available to convert, and how much aromatase activity is happening in the body. Both factors shift with age, body composition, and overall health.
Why Body Fat Matters
Fat cells are the primary source of aromatase in men, so body composition has a direct influence on estrogen production. Men with obesity have higher aromatase levels in their fat tissue compared to lean men. That elevated aromatase activity is also linked to insulin resistance and blood sugar problems, suggesting that local estrogen production in fat tissue contributes to metabolic issues beyond just hormone balance.
This creates a feedback loop worth understanding. More body fat means more aromatase, which converts more testosterone into estrogen. That shift can lower available testosterone while raising estradiol, potentially worsening both hormonal balance and metabolic health simultaneously. Losing fat tissue can help interrupt this cycle by reducing the total amount of aromatase the body produces.
Estrogen’s Role in Male Bone Health
Estrogen is the primary regulator of bone maintenance in adult men. Research published in The Journal of Clinical Investigation found that when estradiol drops below 10 pg/mL, bone breakdown increases dramatically, regardless of testosterone levels. At severely low estradiol levels (below about 3 pg/mL), bone loss accelerated even further, and this effect was completely independent of how much testosterone was present.
The protective threshold appears to be estradiol above 10 pg/mL combined with testosterone above 200 ng/dL. Above those levels, bone density stays relatively stable. Below them, the skeleton starts losing mineral content. This is one reason why men with very low estrogen are at real risk for osteoporosis, a condition many people mistakenly think only affects women.
Effects on Sexual Function
Estrogen’s relationship with male sexual function follows a U-shaped curve: too little is a problem, and too much is also a problem. In men with low testosterone (below 300 ng/dL), having estradiol levels above 5 ng/dL was associated with markedly higher sexual drive. And when researchers gave men an aromatase inhibitor that blocked estrogen production entirely, libido dropped, confirming that some estrogen is necessary for sexual desire.
On the other end, continuously elevated estradiol in men with normal testosterone decreased sexual interest, fantasy, masturbation, and erections. High estradiol is also independently associated with erectile dysfunction, separate from the effects of low testosterone. One mechanism behind this involves estradiol increasing the permeability of blood vessels in the penis, which can cause blood to leak out during an erection rather than staying trapped to maintain firmness.
Brain Function and Mood
Estrogen receptors are widespread in the male brain, and estradiol appears to influence mood through its effects on the serotonin system. A study measuring brain receptor activity in healthy men found that estradiol levels were positively correlated with the density of a key serotonin receptor in the brain’s outer layer. Testosterone showed no independent effect. Since serotonin pathways are central to mood regulation, anxiety, and cognitive function, this suggests estradiol plays a meaningful role in male emotional well-being that operates separately from testosterone’s effects.
Serotonin-producing neurons project from deep brain structures out to practically every region involved in emotion and cognition. When estradiol influences how these neurons function, the effects can ripple across mood, stress response, and mental clarity.
Heart and Blood Vessel Health
Estrogen has protective effects on male cardiovascular health. It helps limit harmful remodeling of the heart and blood vessels, and estrogen deficiency in men is associated with both premature atherosclerosis (hardening of the arteries) and disrupted cholesterol metabolism. Research has also found that men with cardiovascular disease tend to have lower levels of both testosterone and estrogen compared to healthy men, pointing to estrogen as part of the body’s cardiovascular defense system rather than just a reproductive hormone.
Signs of Too Much Estrogen
When estradiol rises above normal range in men, the most recognizable sign is gynecomastia, the development of breast tissue. Symptoms include swelling in the chest area, breast tenderness, and nipple sensitivity. In teenagers going through puberty, this can also involve pain. Other signs of elevated estrogen include water retention, mood changes, and reduced sexual interest or erectile difficulties.
Common causes of elevated estrogen include excess body fat (due to increased aromatase activity), liver conditions that impair estrogen clearance, certain medications, and rarely, estrogen-producing tumors in the adrenal glands or testes.
Signs of Too Little Estrogen
Low estrogen in men is less commonly discussed but carries real consequences. Symptoms include decreased sex drive, increased belly fat, bone loss, and a higher risk of osteoporosis over time. Hypogonadism, a condition where the body produces insufficient sex hormones, is one of the main causes of low estrogen in men since there’s less testosterone available for conversion.
Men on aromatase inhibitors or certain testosterone replacement protocols that suppress estrogen conversion can also end up with estradiol levels that are too low, which may explain why some men on hormone therapy still feel off despite having adequate testosterone numbers.
How Estrogen Levels Are Tested
If you need your estradiol checked, the testing method matters. The recommended approach is a blood test using a technique called LC-MS/MS (liquid chromatography with mass spectrometry), which provides accurate measurements at the lower concentrations typical in men. Standard immunoassay tests, the kind that work well for premenopausal women with higher estrogen levels, are unreliable for men. They can produce inaccurate readings at male-range concentrations and should not be used.
Testing is typically ordered when men show symptoms of either estrogen excess (breast tissue growth being the most common trigger) or estrogen deficiency (low libido, unexplained bone loss, or increasing body fat despite stable habits). The normal reference range for adult men is 20 to 50 pg/mL, though the optimal level for any individual depends on their testosterone level and overall clinical picture.