Gonadotropin-releasing hormone (GnRH) agonists and antagonists belong to a group of hormone drugs
called GnRH analogues.
Gonadotropin-releasing hormone agonists
Gonadotropin-releasing hormone antagonists
Some GnRH analogues are taken as nasal sprays and some are injected under the skin.
How It Works
Daily GnRH agonist
injections overstimulate the
pituitary gland, triggering production of more
luteinizing hormone (LH) and
follicle-stimulating hormone (FSH) than normal, which
makes the pituitary gland temporarily shut down. The "disabled" pituitary gland
then stops producing LH and FSH, which in turn stops
GnRH antagonist injection is a recent addition to infertility
treatment. While agonists act over several days to stop ovulation, antagonists
act almost immediately by blocking the effect of GnRH on the pituitary gland.
Because an antagonist stops the pituitary from making LH within an hour or two,
it doesn't have to be used for as many days as an agonist does.
Why It Is Used
GnRH analogue treatment is used to
"shut down" the
pituitary hormones that control the
infertility concerns, a GnRH analogue (agonist or antagonist) is used:
- To closely time and control ovulation before an
assisted reproductive technology (ART) procedure by
shutting down the
pituitary gland. This is called "pituitary
down-regulation." At the same time or afterward, an ovulation-stimulating
medicine is used to trigger ovulation, with the goal of harvesting good-quality
eggs on a predictable schedule. Increasing numbers of doctors are now using a
GnRH antagonist (instead of a GnRH agonist) at the same time that ovulation medicine is used, quickly
suppressing the luteinizing hormone that can cause early
- To closely time ovulation before some
insemination procedures, when unpredictable ovulation
would make it hard to know when to introduce sperm into a woman's
How Well It Works
GnRH analogues (agonists and
antagonists) predictably stop ovulation and menstruation. Agonists take more
days of treatment than antagonists do to shut down the ovaries.
Controlling ovulation timing before an infertility procedure. Shutting down the
pituitary with GnRH analogue treatment, paired with a
hormone to stimulate egg production, lowers the chance that an ART procedure
will be canceled because of early ovulation. For controlling egg production
before an infertility treatment, a longer course of GnRH agonist treatment has
been shown to produce higher pregnancy and live birth rates, when compared with
a short course of doses.1
When paired with ovulation-stimulating
treatment, GnRH analogues don't cause low-estrogen symptoms. But when GnRH
analogues are taken alone, they produce a temporary condition similar to
menopause, with many of the same effects.
Side effects that go away when a GnRH agonist is
At first, GnRH antagonist treatment
can cause headache, nausea, or swelling, redness, or itching at the injection
See Drug Reference for a full list of side effects. (Drug
Reference is not available in all systems.)
What To Think About
Before insemination, GnRH analogue
treatment paired with an ovulation-stimulating treatment increases the risk of
conceiving a multiple pregnancy, which is dangerous for a mother and her
fetuses. In the case of an assisted reproductive technology such as
in vitro fertilization, this risk is controlled by
limiting the number of fertilized eggs that are transferred to the
Drawbacks of GnRH analogue treatment are menopausal
symptoms and cost of the medicine.
Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.
Burney RO, et al. (2007). Infertility. In JS Berek,
ed., Berek & Novak's Gynecology, 14th ed., pp.
1185-1275. Philadelphia: Lippincott Williams and Wilkins.