Stress Puts Double Whammy On Reproductive System, Fertility

http://www.sciencedaily.com/releases/2009/06/090615171618.htm

ScienceDaily (June 29, 2009) — University of California, Berkeley, researchers have found what they think is a critical and, until now, missing piece of the puzzle about how stress causes sexual dysfunction and infertility.

Scientists know that stress boosts levels of stress hormones - glucocorticoids such as cortisol - that inhibit the body's main sex hormone, gonadotropin releasing hormone (GnRH), and subsequently suppresses sperm count, ovulation and sexual activity.

The new research shows that stress also increases brain levels of a reproductive hormone named gonadotropin-inhibitory hormone, or GnIH, 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 (RFRP), puts the brakes on reproduction by directly inhibiting GnRH.

The common thread appears to be the glucocorticoid stress hormones, which not only suppress GnRH but boost the suppressor GnIH - a double whammy for the reproductive system.

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The conclusions are based on experiments in rats and inferences from the effects of the hormone in birds. But if this new reproductive hormone acts the same way in all mammals, researchers say the finding could not only change the way physicians look at human reproductive problems, but also affect how breeders approach animal husbandry and captive breeding programs for endangered species.

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