Estrogen in Men: Why Men Need Estradiol

Yes, and that is by design. Estrogen, more precisely estradiol, is not a purely female hormone. Every man produces it, mostly from his own testosterone via the enzyme aromatase. In men, estradiol is involved in bone, libido, brain, fat distribution and even fertility. Interestingly, the measured estradiol levels of older men can on average lie above those of women after menopause. So estrogen in men is not an accident but a necessary messenger in a finely tuned network. The question is never whether a man has estrogen, but whether the amount fits the rest of his hormone picture.

Aromatase is an enzyme that converts testosterone into estradiol, turning a male hormone into a supposedly female one. This enzyme sits in fat tissue, in the brain, in bone and in the testes, among other places. In men this is the main pathway by which estrogen is formed. The more fat tissue a man carries, the more aromatase is active and the more testosterone can be converted into estrogen. This explains why excess weight can shift the ratio of testosterone to estrogen. Aromatase is therefore a central regulator that helps determine how much of each hormone ends up in the body.

Because many effects attributed to testosterone actually run through estradiol. A controlled study from Boston in healthy men aged 20 to 50 suggests that the increase in body fat was mainly due to the missing estradiol, while muscle mass and strength depended on testosterone. Both hormones contributed to libido. Because the hormone situation in this study was created with medication, the results cannot be transferred one to one to older men in everyday life. Estradiol can also be crucial for bone in men. In the few men described worldwide whose bodies cannot produce estrogen or cannot respond to it, the growth plates stayed open despite high testosterone levels and osteoporosis developed early. These are individual cases, not a body of study evidence. So in men estradiol is not a by-product but an independently important messenger for bone, libido and brain.

A persistently high estrogen level relative to testosterone can have unwanted consequences in men. Discussed effects include enlargement of breast gland tissue, that is gynecomastia, fluid retention, a dampened control of the testes and mood changes. A frequent reason for a shifted ratio can be increased belly fat, because that is where a lot of aromatase sits. Medications, liver disease, alcohol and hormonal disorders also come into question. The key point is the framing: it is not a high absolute value that is the problem, but the imbalance. And the first lever is usually not a drug against estrogen, but work on weight and lifestyle. If you have symptoms, this should be assessed by a doctor.

Yes, and this is often overlooked. Too low an estradiol level in men can be linked to declining libido, worse mood, more belly fat and above all bone loss. In a large observational study of older men, those with the lowest available estradiol had roughly a one and a half fold increased risk of fractures. The risk was highest when low estradiol, low testosterone and a high binding protein came together. This is clinically relevant because some men, hoping for more testosterone, suppress their estrogen with so-called aromatase inhibitors. Studies suggest that this can worsen bone density. So with estradiol the rule is not the lower the better, but balance is what counts.

They are not an opposing pair but two sides of the same metabolic pathway. Part of testosterone is continuously converted into estradiol via aromatase. The two hormones share tasks: testosterone stands more for muscle, strength and drive, estradiol more for bone, fat distribution and a large part of libido. Anyone who looks only at testosterone misses that many of its effects only arise through estradiol. That is why the single value is not decisive, but rather the ratio and the interplay of the two. It makes sense to assess both hormones together.

In most cases this is not advisable, except with a clear medical indication. Aromatase inhibitors block the conversion of testosterone into estradiol and raise the testosterone value, but at the same time they lower estradiol. Controlled studies in older men showed that this blockade tended to worsen bone density at the spine, because the protective estradiol effect was lost. In men estradiol is important for bone, and an artificially lowered level can weaken this protection. Aromatase inhibitors are prescription-only medicines. They have their established place in entirely different treatment situations that have nothing to do with the topic of this article and belong exclusively in specialist medical hands. In Germany they are not approved for raising the testosterone value in men, so use in this context would be off-label. They are not intended for self-optimization.

A shifted ratio of estrogen to testosterone can contribute to an enlargement of breast gland tissue, the so-called gynecomastia. However, this is rarely a matter of the absolute estrogen value alone. Often the ratio of the two hormones plays a role, frequently in connection with excess weight, certain medications, liver disease or hormonal disorders. A visible or palpable change of the breast in men always belongs in medical hands, before you think about weight or hormones. Behind an enlargement of the breast there can also be causes that need to be recognized quickly, such as a tumor of the testis that produces hormones or, rarely, breast cancer in men. Have it assessed immediately if a swelling affects one side only, if it is firm or painful, if it grows rapidly, if skin or nipple change or fluid leaks, and with any palpable change of a testis. We cover this topic in depth in a dedicated article on the hormonal causes of gynecomastia.

A central one. Fat tissue, especially belly fat, contains a lot of aromatase. The more this fat increases, the more testosterone can be converted into estradiol. At the same time the shifted hormone picture can dampen the higher-level control of the testes, so that less new testosterone is produced. This can create a cycle in which more belly fat shifts the hormone picture further toward estrogen. This is not bad news, because it also means that weight loss can move this ratio in a more favorable direction. With the topic of estrogen in men, weight can be the first sensible starting point for many men.

You should have a doctor assess a visible or palpable breast enlargement, persistent loss of libido, unexplained low mood, an unfulfilled wish to have children or signs of bone loss. Anyone considering testosterone therapy or aromatase inhibitors should also not change their estrogen on their own. Both are prescription-only. Important if you want children: testosterone given from outside can shut down the body's own control of the testes and thereby suppress sperm production. This effect can last for months to years and does not always reverse completely. If you want children, a semen analysis and an andrological workup therefore come first, before any hormone is given. Behind symptoms there can be treatable causes, such as excess weight, liver disease, certain medications or a hormonal disorder. It makes sense to measure testosterone and estradiol together and to look at the whole system rather than a single value. This text does not replace a medical examination.