Chronic gonadotropin-releasing hormone agonist treatment suppresses ovulation and sexual behavior in group-living female rhesus monkeys.

The sexual behavior of six adult rhesus females was observed with each of four males prior to, during, and following a 90 day treatment with 20 micrograms/day of a gonadotropin releasing-hormone (GnRH) agonist (WY-40972). All females ovulated, approached males and copulated during an untreated cycle. No ovulations occurred during agonist treatment and all females showed reduced sexual interest during the last 25 treatment days. Three females showed elevated estradiol and copulated during the first 10 days of agonist treatment, but never showed similar levels of estradiol or copulation during the rest of treatment. Within 34 days after agonist treatment, all females initiated proximity to males, copulated, and ovulated. All females became pregnant on their second ovulation after agonist treatment. This demonstration that inhibition of ovulation with a GnRH agonist decreased rhesus female sexual initiation, demonstrates the importance of ovarian hormones to female sexual motivation and suggests that the changes in human female sexual interest should be evaluated during the development of agonist-based contraceptives.