Complete ovarian unresponsiveness to hMG stimulation after prolonged GnRH analogue administration

GnRH agonists (GnRH-a) have recently been shown to exert an inhibitory effect on human reproductive functions, the mechanism for this effect being attributed solely to the desensitization of the pituitary gonadotropin receptors to GnRH-a. We present two cases where chronic treatment with a GnRH-a caused complete suppression of ovarian activity in vivo. The effect could not be counteracted by large hMG doses and resulted in high FSH plasma concentrations. Normal ovarian activity was restored only after withdrawal of GnRH-a.