Irregular or limited development of follicles can occur during stimulated cycles (using menotropins).
At the onset of a menstrual flow follicles prepared for the cycle have begun to develop (FSH normally rises a few days prior to the onset of menstrual flow). In some cycles of COH only 1 or 2 eggs will mature. At the beginning of these cycles, one or two follicles appear to have developed enough FSH receptors and blood supply to “outcompete” the other follicles for FSH (these few follicles apparently take up the majority of the circulating FSH). This can be an expensive and disappointing way of developing 1 mature egg since most women use menotropins for ovulation enhancement (maturation of more than one mature egg per cycle) rather than ovulation induction.
GnRH agonists (such as Lupron and Synarel) suppress ovarian follicular development when they are started about 1 week prior to the expected menstrual flow so that they “even out” follicle development at the onset of the upcoming cycle. This improves the chance for multiple egg maturation when the patient has a history of irregular egg development during menotropin therapy.
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