While estrogen is generally known as a female sex hormone. But a man's body also produces small amounts of estrogen, which is important for normal development and function of the male reproductive system 1. However, an abnormally high level of estrogen can have major effects on a man’s body, possibly interfering with his fertility and sexual function, and potentially raising his risk of certain chronic diseases. Fertility problems, breast enlargement and erectile dysfunction are among the signs and symptoms that might signal a high estrogen level in a man.

Fertility Problems

A man's fertility depends partly on having enough sperm in an ejaculate to fertilize an egg. According to the World Health Organization, a normal sperm count is at least 15 million per milliliter of semen 2. If a man's sperm count is too low, he may experience reduced fertility. Laboratory research has shown that male laboratory animals dosed with estrogen can cause infertility. For example, a study published in the September 2001 issue of the "Journal of Endocrinological Investigation" found that administration of estrogen to male rats led to reduced testis weight and sperm production, compared to animals not treated with estrogen 3. The effect of estrogen on human male sperm counts hasn't been studied directly, but preliminary research such as that published in the December 2002 issue of "Fertility and Sterility" suggests that estrogen-like environmental compounds might contribute to low sperm counts in some infertile men 4.

Erectile Dysfunction

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A shift in the balance of testosterone to estrogen in a man's body could cause erectile dysfunction, which is difficulty achieving or maintaining an erection 5. A review article published in the July 2011 issue of the "Asian Journal of Andrology" evaluated research examining whether a relative increase in the estrogen to testosterone ratio in older men contributes to erectile dysfunction in this population 5. As men age, testosterone levels gradually decrease, potentially causing an imbalance of estrogen and testosterone. The authors concluded that this type of hormone imbalance is a likely contributor to loss of interest in sexual activity and higher rates of erectile dysfunction in older men, compared to younger men. Some laboratory studies, which found decreased mating ability in male laboratory animals treated with estrogen, also suggest that too much estrogen might cause erectile problems.

Breast Growth

Exposure to excess estrogen can cause abnormal growth of breast tissue in men. This condition, called gynecomastia, typically involves both breasts. Certain medications, such as estrogen-like compounds used to treat prostate cancer, may cause this problem. Unintended exposure to creams or other products containing estrogen can also cause breast growth, as shown in a study published in the April 2000 issue of "Pediatrics." The researchers reported that prepubertal boys accidentally exposed to estrogen-containing cream experienced high estrogen levels and gynecomastia 7. In most cases, once the source of estrogen is removed, the breasts return to normal size.

Cardiovascular Problems

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Some research suggests that relatively high estrogen level in men might raise the risk for circulatory problems, heart attack and stroke. A small study published in the April 2007 issue of "Neuro Endocrinology Letters" reported that estrogen levels were higher in men who had experienced a heart attack, compared to men who did not have coronary artery disease 8. Another study published in the March 2007 issue of "Neurology" found that men aged 70 and older with high estrogen levels could have a higher risk of stroke 9. However, more studies are needed to confirm a link between high estrogen levels in men and these conditions.

Warnings and Precautions

See your doctor as soon as possible if you experience signs or symptoms that might indicate a high estrogen level. Your doctor can check your blood hormone levels to determine whether your estrogen is elevated, or if there is an imbalance between your estrogen and testosterone levels. In some cases, excess estrogen could indicate a hormone-secreting tumor or another serious medical problem, so it's important not to ignore your symptoms.

Reviewed and revised by: Tina M. St. John, M.D.