GnRH antagonist vs GNRH agonist protocol: which patients does it benefit?

This study compared gonadotropin-releasing hormone (GnRH) agonist versus GnRH antagonist protocols for stimulating the ovaries. It found that women under 30 years with high ovarian reserve benefited from the antagonist protocol, while the agonist protocol was better for women over 40 years or with low ovarian reserve.

GnRH is a reproductive hormone that affects the pituitary gland in the brain. GnRH is released in rhythmic pulses. Slow pulses cause the pituitary to release follicle-stimulating hormone (FSH), while faster pulses cause the pituitary to release luteinizing hormone (LH). A surge in LH is responsible for triggering ovulation.

The infertility treatment in vitro fertilization (IVF) involves stimulating and collecting multiple eggs. It is important to prevent a natural LH surge from triggering ovulation before the scheduled egg collection.

There are two methods to prevent a natural LH surge, GnRH agonist and antagonist. GnRH agonist acts like GnRH. When GnRH agonist is first given, it causes the pituitary to become more active. However, after a while, the pituitary stops responding to the constant GnRH agonist. By contrast, the GnRH antagonist directly blocks the pituitary from responding to GnRH. Both GnRH agonist and antagonist can prevent an LH surge during IVF treatment. It is not clear which method leads to better IVF outcomes.

This study includes records from 4,402 patients undergoing their first egg collection cycle. 2,762 patients used GnRH agonist, and 1,640 used the GnRH antagonist protocol. The study followed up to three embryo transfers from the same egg collection.

Ovarian hyperstimulation syndrome (OHSS) occurs when the ovaries respond too vigorously to stimulation. Patients using GnRH agonist had significantly more embryo transfers canceled due to OHSS risk (49.6% vs. 37.3%).

Patients using GnRH agonist had significantly more eggs collected (13.1 vs. 11.0) and a significantly higher birth rate (50.0% vs. 45.3%). However, there was no difference in the birth rates after adjusting for factors including age and length of infertility.

Ovarian reserve is an estimate of many eggs are available and can be measured by the antral follicle count (AFC). For patients with a low ovarian reserve (AFC below 7), using GnRH antagonist protocol reduced the chances of live birth by 38% compared to GnRH agonist. For women with a moderate ovarian reserve (AFC between 7 and 24), the two protocols led to similar live birth chances. For women with a high ovarian reserve (AFC above 24), GnRH antagonist increased the chances of birth by 43%. GnRH agonist significantly increased the chance of birth for women over 40 years old.

This study found that the GnRH agonist protocol was better for women over 40 or those with low ovarian reserve. The GnRH antagonist protocol led to better outcomes for women with a high ovarian reserve.

The patients using the two protocols had different characteristics. Studies, where patients are randomly assigned to a treatment, are more informative than studies like this one, which uses patient records.