Men produce estrogen by converting testosterone and other androgens through an enzyme called aromatase. This process, called aromatization, happens in several tissues throughout the body and produces roughly 50 micrograms of estradiol per day. Far from being exclusively a “female hormone,” estrogen plays essential roles in male bone health, sexual function, and sperm production.
The Aromatase Conversion Process
Men don’t have a dedicated estrogen-producing organ the way women have ovaries. Instead, the male body takes androgens it already makes (primarily testosterone and androstenedione) and converts them into estrogen using the aromatase enzyme. This conversion involves three consecutive chemical reactions that reshape the steroid molecule, transforming testosterone into estradiol (the most potent estrogen) and androstenedione into estrone (a weaker form).
Interestingly, the conversion of androstenedione to estrone happens at a higher rate than the conversion of testosterone to estradiol. Both pathways contribute to the total circulating estrogen in the male body, but the androstenedione pathway is the more active of the two. The transfer rate for androstenedione to estrone in men is about 1.35%, compared to a lower rate for testosterone to estradiol. Men actually convert androgens to estrogens at roughly double the rate women do through these peripheral pathways.
Where Estrogen Is Made in the Male Body
Only about 10 to 20% of a man’s daily estradiol comes directly from the testes. That works out to about 5 to 10 micrograms per day. The remaining 80 to 90%, or roughly 40 to 45 micrograms, is produced in peripheral tissues where aromatase is active: fat tissue, muscle, brain, liver, breast tissue, and bone.
Fat tissue deserves special attention here. Adipose cells are one of the most significant sources of aromatase activity in men, and the more fat tissue you carry, the more aromatase is available to convert testosterone into estradiol. This creates a compounding effect in men with obesity: increased fat mass drives up aromatase activity, which converts more testosterone to estrogen, which in turn can promote further fat storage. The result is lower circulating testosterone and higher estrogen levels, a pattern well documented in obese men.
What Estrogen Does in the Male Body
Estrogen is not just a byproduct of testosterone metabolism. It serves several functions that men cannot maintain without it.
Estradiol is essential for modulating libido, erectile function, and sperm production. In men with low testosterone (below 300 ng/dL), sexual drive was markedly higher when estradiol levels were above 5 ng/dL, suggesting that estrogen works alongside testosterone to maintain desire. In one case involving a man who couldn’t produce aromatase at all, neither testosterone nor estrogen alone was enough to restore libido. Both hormones together were required.
For sperm production, estrogen acts as a survival signal for developing sperm cells. Even low concentrations of estradiol can enhance germ cell production by preventing those cells from dying off prematurely. An abnormal testosterone-to-estradiol ratio (below 10:1) has been linked to poorer sperm quality, including reduced concentration, motility, and normal shape. Correcting that ratio can improve sperm retrieval rates by about 1.4-fold in men with severe sperm production problems.
Estrogen also plays a critical role in bone health. Without adequate estrogen, men experience accelerated bone loss and are at higher risk for osteoporosis, a condition most people associate exclusively with women.
How the Body Regulates Estrogen Levels
Estrogen participates in a feedback loop that controls its own production. The hypothalamus releases a signaling hormone that tells the pituitary gland to secrete two hormones (LH and FSH) that stimulate the testes. The testes then produce testosterone, some of which gets converted to estradiol. When estradiol levels rise high enough, it signals back to the hypothalamus and pituitary to slow down, reducing the drive for more testosterone production. Men who lack aromatase entirely tend to have elevated levels of FSH, confirming that estrogen is a necessary part of this braking mechanism.
Normal Estrogen Levels in Men
The typical reference range for serum estradiol in men is 10 to 40 pg/mL. This is considerably lower than premenopausal women, but it’s not negligible, and maintaining levels within this range matters for health.
As men age, both testosterone and estrogen production decline. However, testosterone drops more steeply than estrogen does, which shifts the ratio between the two hormones. Older men tend to have a lower testosterone-to-estradiol ratio compared to younger men, meaning estrogen becomes relatively more prominent even as its absolute levels decrease.
What Happens When Estrogen Is Too High or Too Low
Low estrogen in men can cause decreased sex drive, increased belly fat, bone loss, and a higher risk of cardiovascular disease. These symptoms often overlap with low testosterone, which makes sense given that estrogen is derived from testosterone and the two hormones work together.
High estrogen presents a different set of problems. Excess estradiol can lead to breast tissue enlargement (gynecomastia), erectile dysfunction, infertility, and depression. In younger males, elevated estrogen may contribute to delayed puberty and shorter adult height by causing growth plates to close prematurely. High estrogen in men has also been linked to increased migraine frequency and may signal underlying conditions like liver cirrhosis, thyroid overactivity, or tumors of the adrenal glands or testes.
How Body Fat Shifts the Balance
Because fat tissue is the largest peripheral source of aromatase, body composition has a direct and measurable effect on a man’s estrogen levels. Weight gain increases aromatase activity, which pulls more testosterone out of circulation and converts it irreversibly into estradiol. This is a one-way reaction: once testosterone becomes estradiol, it cannot be converted back.
The practical implication is straightforward. Men who carry significant excess body fat often show a hormonal profile of lower testosterone and higher estrogen, which can worsen symptoms in both directions. Reducing body fat lowers aromatase activity and can help restore a healthier hormone balance without any medical intervention. This relationship between adiposity and estrogen production is one of the most modifiable factors in male hormonal health.