When patients receive injections of the fertility drug FSH (Follistim, Gonal-F, Repronex, Bravelle, Menopur) for ovarian stimulation in assisted reproductive technology procedures, it is important to insure that ovulation does not occur before the eggs mature and are retrieved.  If ovulation occurs prior to egg retrieval, the stimulation cycle will be lost.

Gonadotropin releasing hormone (GnRH) is produced by the hypothalamus and causes the pituitary to produce FSH.  These relationships are part of the hypothalamic-pituitary-adrenal axis, which coordinates the production of various hormones including leutinizing hormone (LH). LH causes release of the mature eggs from the ovarian follicles.

Lupron (leuprolide acetate) and Synarel are GnRH agonists, which means that they work at the level of the  pituitary to release FSH and LH, thereby depleting the body of FSH and LH and causing a state known as down regulation. When a woman is down regulated, FSH must be administered by injection to cause ovarian development. Since her own hormones are depleted, she cannot interfere with the egg development or cause premature release of the eggs before the scheduled egg retrieval.  When the follicles mature, an injection of LH or hCG is required to cause ovulation, and prepare the eggs for retrieval. The fertility specialist controls the process of follicular development by administering various hormones.

Lupron and Synarel are given according to protocols and are usually started in the cycle prior to the IVF treatment cycle.  Lupron causes an initial increase (flare effect) in FSH production that is useful in some “poor responder” patients.

Antagon and Cetrotide are also used to stop the production of LH and FSH albeit by a different mechanism.  These fertility drugs are known as GnRH antagonists because they directly block the action of GnRH and produce a more immediate and profound blockade of GnRH. This blockade stops the production of FSH and LH.  The advantage of an antagonist is that they are given for shorter periods.  As is the case with Lupron, ovulation cannot occur until external LH or hCG (the body responds to hCG in the same manner as LH) is administered.

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