Men Need Estrogen Too, Study Determines Mice Need Hormone To Prevent Reproductive Problems

Most people consider estrogen a female hormone, but men make it too. A new study suggests one reason why: Estrogen may help men stay fertile by preventing a plumbing problem in the reproductive system.

The study, done in mice, marks the first time scientists have specified a detailed role for estrogen in the male reproductive tract.

The topic is timely because of recent assertions that some environmental chemicals may be reducing sperm counts and otherwise harming male reproductive health by disrupting hormonal signaling. The new study doesn’t address whether that’s true, but it may help research into the issue.

It’s unclear whether estrogen-related defects cause any significant amount of infertility in men. But the research might help scientists develop a male contraceptive, said the study’s lead author, Rex Hess of the University of Illinois.

He and colleagues present the work in today’s issue of the journal Nature.

Estrogen acts by binding to structures called receptors in cells. here are at least two kinds of estrogen receptors, and last year scientists reported that male mice that lacked one kind - and so couldn’t respond fully to estrogen - were infertile. Their sperm were defective and sperm counts were low.

That showed estrogen does something to preserve fertility in male mice, and perhaps men as well. The new work follows that up.

Researchers used mice that lacked one of the estrogen receptors. They found that tubes that transport sperm and fluid in these mice fail to do an important job: absorbing a lot of that fluid. That absorption concentrates substances in the fluid that help the sperm mature, and also concentrates the sperm to ensure a large dose for ejaculation.

The lack of sperm concentration makes sperm counts drop in mice, Hess said. So it’s worth studying whether the same process is causing reported declines in sperm counts in men, he said.

Another possibility in the mice is that the concentration of the substances that help the sperm mature is abnormal, leading to defective sperm, said Dennis Lubahn of the University of Missouri in Columbia, another study author.