How stress causes infertility

BERKELEY, Calif., June 16 (UPI) -- Researchers at the University of California, Berkeley, say they found how stress causes sexual dysfunction and infertility.

Lead author Elizabeth Kirby, a graduate student, said scientists know stress boosts levels of stress hormones -- glucocorticoids such as cortisol -- that inhibit the body's main sex hormone, gonadotropin releasing hormone. This subsequently suppresses sperm count, ovulation and sexual activity.

The study, published in the journal Proceedings of the National Academy of Sciences, shows that stress also increases brain levels of a reproductive hormone named gonadotropin-inhibitory hormone, or gonadotropin-inhibitory hormone, discovered nine years ago in birds and known to be present in humans and other mammals.

This small protein hormone, a so-called RFamide-related peptide, puts the brakes on reproduction by directly inhibiting gonadotropin releasing hormone, Kirby said.

"We know stress affects the top-tier reproductive hormone, gonadotropin releasing hormone, but we show, in fact, that stress also affects another high-level hormone, gonadotropin-inhibitory hormone, to cause reproductive dysfunction," lead author Elizabeth Kirby, a graduate student, said in a statement. "This work provides a new target for researchers, a new way to think about infertility and dysfunction."

If this reproductive hormone acts the same way in all mammals, the finding could change the way physicians look at human reproductive problems, the researchers said.