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In the past, most in-vitro fertilization (IVF) centres used pituitary down-regulation with gonadotrophin-releasing hormone (GnRH) agonists to prevent a premature LH surge and premature ovulation and luteinization. However, this required at least 7-14 days of GnRH agonist pretreatment.
The rational approach
This is why researchers developed molecules which would cause an immediate blockage of the GnRH receptors on the pituitary gland, to stop the pituitary from producing gonadotropins instantly. This was felt to be a more rational approach , as these would induce instant downregulation , and prevent a spontaneous LH surge more effectively .
Brand names of the GnRH antagonists include Antagon and Cetroride. Thus , treatment with the antagonist can be limited to only those 4-6 days when high oestradiol levels may induce a premature LH surge. This means they are usually started after the HMG superovulation has been given for 3-4 days - usually Day 7 or 8 of the cycle.
However, clinical experience with GnRH antagonists in IVF treatment thus far has shown mixed results, with no evidence that they are any better than the traditional GnRH analogues. They seem to be as good; but are more expensive; and do offer an additional option which may be useful in selected patients.