How are GnRH modulators used in ovarian stimulation during IVF?

• A. They are not used in IVF
• B. Use GnRH agonist alone throughout cycle
• C. Use GnRH modulators to prevent premature LH surge, often with either agonist long suppression or antagonist short protocol
• D. Use only progestin to suppress cycle

Answer: (C)

Preventing an early LH surge during ovarian stimulation is essential in IVF. GnRH modulators achieve this by controlling the pituitary to keep LH (and FSH) from triggering premature ovulation, so you can grow multiple follicles safely.

There are two common approaches. One uses a GnRH agonist to create long-term suppression of the pituitary. You start the agonist in the luteal phase of the preceding cycle, which desensitizes the pituitary and stops natural FSH/LH. Then you begin controlled ovarian stimulation with exogenous gonadotropins while the pituitary remains suppressed. When the follicles are ready, you trigger final maturation and retrieve the eggs.

The other approach uses a GnRH antagonist in a shorter, more flexible protocol. Gonadotropins are started early, and an antagonist is added once the follicles reach a certain size to block the LH surge. This prevents premature ovulation without as long a course of suppression, and it can reduce the risk of certain side effects and OHSS in some patients.

Why the other ideas aren’t the standard: a GnRH modulator is indeed used in IVF, not avoided. Using progestin alone to suppress the cycle isn’t the typical method for preventing the LH surge during stimulation. And saying agonist is used alone throughout the cycle ignores the need for gonadotropin stimulation to develop multiple follicles. The key concept is preventing the premature LH surge, with either a long agonist suppression or a shorter antagonist approach.