By Neus Ferrando Gilabert BSc, MSc (embryologist).
Last Update: 04/29/2014

GnRH antagonists are used in assisted reproductive treatments such as conventional in vitro fertilisation or ICSI.

These drugs are used to avoid the premature luteinization of follicles and control the ovulation date so that it does not occur too early.

GnRH antagonists

Effects

GnRH antagonists are used to trigger ovulation in assisted reproductive treatments such as AI, IVF, or ICSI.

Its administration may cause the following effects:

  • GnRH antagonists binds to the receptor, therefore GnRH cannot bind (compet
    itive blockage). Receptors are placed in the surface of the pituitary gonadotrope cells.
  • It blocks the synthesis of gonadotropins (FSH and LH) by the hypophysis, since it blocks GnRH receptors.
  • They have an immediate onset of action.
  • It prevents the flare-up effect of GnRH agonists to occur.

Indications

Prescription of GnRH antagonists is indicated in the following cases:

Administration of GnRH antagonists

Advantages

The advantages of this medicine in assisted reproduction cycles are mentioned hereafter:

  • It causes the immediate cancellation of LH serum levels, preventing thus premature ovulation.
  • It implies a shorter duration of the ovulation induction treatment.
  • It is usually well tolerated by women. It has few side effects, since the stimulation process is not very aggressive.
  • A lower dose of FSH is administered.
  • It decreases the frequency of ovarian hyperstimulation syndrome (OHSS).
  • Woman’s recovery of the pituitary function occurs faster, which means it will not affect new stimulation treatments in future cycles.
  • It does not cause follicle cysts, since it prevents the flare-up effect which GnRH agonists would cause.

GnRH antagonists. Cetrotide

Disadvantages

The use of GnRH antagonists involves few disadvantages, since it is well tolerated by most women with virtually no contraindications mainly because the stimulation process is not very aggressive.

The only problem is that its pregnancy rate is slightly lower (between 3% up to 5% less) than that obtained by means of ovarian stimulation protocols, where GnRH analogues are used due to the effect of the antagonists on the endometrium, the Fallopian tubes, the follicle, and the oocyte.

Medicines containing GnRH antagonists which are typically prescribed in assisted reproductive treatments are Cetrotide and Orgalutran.

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Authors and contributors

 Neus Ferrando Gilabert
BSc, MSc
Embryologist
Bachelor's Degree in Biology from the University of Valencia (UV). Postgraduate Course in Biotechnology of Human Assisted Reproduction from the Miguel Hernández University of Elche (UMH). Experience managing Embryology and Andrology Labs at Centro Médico Manzanera (Logroño, Spain). More information