GnRH Antagonists

GnRH (Gonadotropin-Releasing Hormone) Antagonists are medications used in controlled ovarian stimulation (COS) during IVF and IUI cycles. They help regulate ovulation timing, prevent premature ovulation, and optimize egg retrieval success.

GnRH Antagonists (e.g., Cetrotide, Ganirelix)

Examples: Cetrotide (Cetrorelix), Ganirelix

How They Work:

Unlike agonists, antagonists work immediately to block LH release, preventing premature ovulation without the initial hormone surge.

Who It’s For:

- Women undergoing IVF or IUI to prevent premature ovulation.
- Women who need a shorter treatment plan than GnRH agonists.
- Women at higher risk of OHSS (PCOS, high follicle count).

How It’s Taken:

• Usually started around day 5–7 of ovarian stimulation.

• Given as a daily injection until the trigger shot.

Success Rates:

• Equally effective as GnRH agonists in preventing premature ovulation.

• Shorter treatment duration than agonists.

Benefits:

- Immediate suppression of LH surge.
- Shorter treatment time compared to agonists.
- Lower risk of OHSS.

Side Effects:

• Mild skin reactions at the injection site

• Nausea, headaches

• Less hormonal suppression than agonists

Final Thoughts:

Both GnRH Agonists and Antagonists are critical in IVF treatments to prevent premature ovulation and optimize egg retrieval.

• Agonists (Lupron) are used for long-term suppression, endometriosis, and Lupron triggers.

• Antagonists (Cetrotide, Ganirelix) offer faster onset, shorter treatment, and fewer side effects.

Doctors choose based on the individual's ovarian response, risk factors, and IVF protocol.