Many people associate estrogen with women and know that it's a female sex hormone that helps regulate a woman's menstrual cycle. Normally, though, a man's body also makes small amounts of estrogen, which is important for normal development and function of the male reproductive system. But when a man is exposed to abnormally high levels of estrogen, it can have major effects on his body, possibly interfering with his fertility and sexual function and potentially raising his risk of certain chronic diseases. If you have questions about estrogen in men and any of its possible effects, talk to your doctor.
A man's fertility depends partly on having enough sperm in an ejaculate to fertilize an egg and produce an embryo. The number of sperm in a normal ejaculate should be at least 30 million and can be as high as 200 million, and if a man's sperm count is too low, he may be infertile. Laboratory research has demonstrated that exposure of male laboratory animals to estrogen can cause infertility. For example, in one study published in the September 2001 issue of "Journal of Endocrinological Investigation," researchers observed reduced testis weights and lowered sperm production in animals treated with low doses of estrogen, compared to controls. Although the effect of estrogen on human male sperm counts hasn't been studied directly, research such as that published in the December 2002 issue of "Fertility and Sterility" suggests that estrogen-like environmental compounds could be responsible for low sperm counts in some infertile men.
A shift in the ratio between testosterone and estrogen in a man's body could cause difficulty in achieving or maintaining an erection. In a review paper published in the July 2011 issue of "Asian Journal of Andrology," researchers evaluated evidence that a change in this ratio, which causes a relative increase in estrogen compared to testosterone, could explain the higher rate of erectile dysfunction in older men in whom testosterone drops with increased age. The study concluded that this is a likely cause. 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.
Exposure of a male to excess estrogen can also cause abnormal growth of breast tissue, called gynecomastia, which usually 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 in the April 2000 issue of "Pediatrics," which reported that three teenage males exposed to estrogen-containing cream had breast enlargement. In most cases, once the source of estrogen is removed, the breasts return to normal.
Some research also suggests that relatively high estrogen in men might raise the risk of circulatory problems, heart attack and stroke. In a study published in the April 2007 issue of "Neuro Endocrinology Letters," researchers found that estrogen levels in men who had experienced a heart attack were higher than in other men, while another study published in the March 2007 issue of "Neurology" concluded that elderly men with high estrogen levels could have a higher risk of stroke. However, more studies are needed to confirm a link between high estrogen in men and these conditions.