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Friday, 18 April 2014

How is ovulation prevented in IVF?

The drama that is enacted in the ovary every month is directed by pituitary (an organ in brain) through messengers FSH and LH (together called Gonadotrophins). The "Director" Pituitary in turn has to act as per the orders of "Grandmaster" Hypothalamus (also a part of brain). Hypothalamus sends its signals to pituitary via messengers called gonadotropin releasing hormones (GnRH). The two medicines used to prevent ovulation during IVF are GnRH analogs and GnRH antagonists.

GnRH analogs (such as Lupride, Buserelin etc.) are substances which have a structure similar to GnRH and cause some response from the pituitary (called flare response) in the form of release of FSH and LH. On being given daily, the flare stops and the pituitary becomes unresponsive and hereafter no release of FSH and LH occurs. This is called down regulation and take about 5 days of injections.

GnRH antagonists (such as Cetrotide and Ganirelix) resemble GnRH molecule but unlike analogs, these elicit no flare response from the pituitary. They are effective immediately in stopping the pituitary from releasing any gonadotropins. 

In IVF, either agonists or antagonists are used alongside ovarian stimulation to prevent premature ovulation from occurring. I will discuss the different protocols used in IVF in my next post....

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