GnRH Agonist

If you and your partner are having unsuccessful fertility treatments, it may be due to a problem with ovulation. IVF and IUI treatments can sometimes be compromised if ovulation does not occur at just the right time.

Many women ovulate prematurely, which lowers their chances of pregnancy through assisted reproductive therapy. GnRH agonists can sometimes help to stop premature ovulation, thus increasing the chances of pregnancy during IVF and IUI treatments.

What are GnRH agonists?

GnRH agonist is a medication that works against GnRH (gonadotropin releasing hormone) in the brain. GnRH works on the pituitary gland, helping it to release follicle stimulating hormone (FSH) and luteinizing hormone (LH).

These hormones play a key role in ovulation. GnRH agonists work to block the action of GnRH, preventing the release of LH and FSH, thus preventing ovulation.

When are GnRH Agonists Used?

GnRH agonists are used to help stop ovulation from occuring too early. When ovulation occurs early, eggs tend to be of a lower quality and less useful for use in:

  • IUI
  • IVF
  • GIFT

GnRH agonists are also used to help treat the growth of the menstrual lining in patients with endometriosis.

How do GnRH Agonists Work?

GnRH agonists work by essentially "shutting down" the pituitary gland. The pituitary gland is a tiny gland located in the frontal portion of your brain, just behind your nose. It secretes LH and FSH to trigger ovulation.

GnRH agonists overstimulate the pituitary, causing it to release more FSH and LH. When it senses this overstimulation, the pituitary gland shuts down, stopping ovulation from occuring.

Types of GnRH Agonists

There are actually two types of GnRH agonists:

  • GnRH Agonists/Anologs: These take several days to work on GnRH in the brain. They can take up to a week or more to stop ovulation.
  • GnRH Antagonists: These work much more quickly to stop ovulation. They are usually given along with ovulation stimulation drugs and can stop premature ovulation in a matter of hours.

How are GnRH Agonists Taken?

GnRH agonists and antagonists are typically given in combination with ovulation stimulation medications. GnRH agonists are given in the form of intramuscular or subcutaneous injections, or as a nasal spray.

They are typically given once or twice a day, for several days, after which ovulation stimulators are administered. GnRH antagonists can be given at the same time as ovulation stimulators.

Side Effects of GnRH Agonists

When taken without ovulation stimulators, GnRH agonists cause similar side effects as incurred with menopause.

Common side effects include: 

  • hot flashes
  • mood swings
  • insomnia
  • headache
  • decreased libido

GnRH antagonists also cause side effects, including headache, nausea, and swelling, itching, and redness and the site of injection.

How Effective are GnRH Agonists?
GnRH agonists are quite effective at preventing premature ovulation, helping to increase the likelihood of pregnancy during IVF and associated treatments.

They work to prevent the release of underdeveloped eggs and instead, promote the release of healthier eggs during ovulation.


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