Whether you are a zebra constantly running from lions or a chemistry major on the brink of failing a course, stress can be a healthy part of life.

But too much stress may negatively affect the way animals — including humans — reproduce, according to a UC Berkeley study published Monday in the Proceedings of the National Academy of Sciences.

"We have found a missing piece of the puzzle by finding the way (stress) affects reproduction at a molecular level," said Daniela Kaufer, UC Berkeley assistant professor of integrative biology and co-author of the study.

In the study, researchers found that the suppressor hormone GnIH, which suppresses sex hormones in the brain, directly affects the process of reproduction.

The study showed that when rats were put under stress, they produced a type of glucocorticoid hormone in high amounts, which, when bonded to GnIH receptors in the brain, increase the amount of the suppressor hormone.

"GnIH is a negative regulator of the sexual reproduction axis," said integrative biology graduate student and co-author Anna Geraghty.

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