New Sex Hormone Found—May Lead to Male Birth Control?

A new human sex hormone has been found, a new study says. The naturally occurring substance could lead to the long-sought male birth control pill, researchers cautiously speculate.

Gonadotropin-inhibitory hormone (GnIH)—first identified in birds about a decade ago—was recently discovered in the hypothalamus of the human brain. The hypothalamus produces hormones that regulate sleep, sex drive, body temperature, and more.

GnIH suppresses another hormone—gonadotropin-releasing hormone (GnRH)—which spurs the release of additional hormones, which prime the body for sex and reproduction. So scientists cautiously suggest that contraceptives based on the newfound hormone could someday be possible. 

"That is an idea we've toyed with," said study co-author George Bentley, a biologist at the University of California, Berkeley. But "we don't know enough about it yet."

Louis DePaolo, the U.S. National Institutes of Health's Reproductive Sciences Branch chief, agreed "it's too premature" to consider a male birth control pill.

GnIH has been known in animals since 2000, and it was known that humans have a GnIH gene, but until now it was a mystery whether humans actually produce the hormone and what its role is.

The researchers, however, extracted GnIH from five human hypthalumuses and proved that the it affects nerve cells that produce the GnRH, the fertility-boosting hormone.

Now Hormone Could Be Cancer Fighter?

But GnIH could be part of new treatments to combat hormone-sensitive cancers, such as breast and prostate cancers, the study said.

(Related: Exploding Bubbles Can Trim Enlarged Prostate.)

Synthetic substances are used today to suppress GnRH, the fertility-boosting hormone. But they come with side effects such as allergic reactions, weight gain, and hot flashes.

Researchers suggest that GnIH, the new hormone, could slow down the reproductive system naturally—and without side effects.

But first "we would have to understand exactly how this works in humans and how it works in concert with other hormones," study co-author Bentley said.

"We've got a long way to go, but I think the fact that it's present in humans could be useful."

NIH's DePaolo, who was not involved in the research, agreed. "We know where GnIH might work. We don't know how important it is, we don't know its role.

"It's got to be important in some form, or why would it be there?"

Research appeared December 22 in the journal PLoS One.

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