Stress is known to decrease fertility and sexual behavior, but researchers thought this was because stress hormones lower levels of a brain hormone called gonadotropin releasing hormone, or GnRH. Biologists now show that stress hormones also boost levels of a hormone that suppresses GnRH — a double whammy. The scientists hope it will be possible to block this hormone, called gonadotropin inhibiting hormone, or GnIH, and restore fertility.