The goal of the first part of the IVF cycle is to mature multiple eggs and then extract
them from the ovaries. There are many different medications that are used during this process.
What are all of these IVF injections?
What do they do in your body? Is one kind any better than another? Stay tuned.
IVF injections can be divided into three groups:
those that prevent ovulation, those that stimulate the maturation of the eggs and those
that and those that do both. Lets talk about the medications that prevent ovulation first.
Why are these medications needed? When the eggs are maturing, the ovaries are producing hormones.
These hormones can cause the pituitary gland to release the hormone, LH, which triggers release
of the eggs. In the early days of IVF, before medications were available to prevent ovulation,
about 25% of IVF cycles were cancelled because of premature ovulation. If the
eggs were released from the ovary before the doctor performed the egg retrieval,
then there were no eggs left to remove. This was an expensive and inconvenient problem.
The medications that are currently used most often to block premature ovulation are called
GnRH antagonists. The brands that are available in the U.S. are called Ganirelix and Cetrotide.
These injections are highly effective and work immediately, from the very first injection.
Antagonists work by blocking the pituitary gland from releasing LH and therefore block ovulation.
Antagonists are usually started after the 5th or 6th day of the stimulation of the
ovaries and continue right up until the day before the last injection.
Before the antagonists were available, another group of medications were used
to prevent premature ovulation in IVF cycles. These medications are known as GnRH agonists.
In the United States, the most commonly used brand is called Lupron. I’ll use Lupron as an
example but the same properties are common to all GnRH agonists. Like the antagonists,
Lupron also works by blocking the pituitary gland from releasing LH,
but before it blocks LH, it actually increases LH release from the ovary. This is known as the flare
effect. The flare effect can result in higher hormone release from the pituitary gland for
several days before it finally starts blocking LH and the levels get lower.
Because of this, women who are using Lupron to prevent premature ovulation must start taking
it a few weeks before they start the fertility injections to stimulate the ovaries. These types
of IVF cycles take a lot longer than ones that use antagonists and have many more days of injections.
In some cases, the extra hormones released from the pituitary during the Lupron flare
phase will cause cysts to develop in the ovaries. Those ovarian cysts also produce
hormones such as estrogen. If this happens, then it may require women to take Lupron for days
or even weeks longer before the fertility injections can be started.
Remember earlier I said that some IVF injections stimulate the ovaries and block premature
ovulation? Lupron is a medication that can be used in that way. For women who don’t respond
well to fertility medications alone, some doctors like to use that flare effect that Lupron has
in order to help stimulate the ovaries initially and then after several days block the premature
ovulation. This is known as the Flare protocol. Which type of medication to block ovulation is
best? When the antagonists first came out, a few studies found that the pregnancy were lower
compared to the agonists like Lupron. However, since then, a few things have changed. First,
doctors got better at learning the optimal way to use fertility medications when using
antagonists. Second, most IVF experts are now freezing all of the embryos from an IVF cycle
and doing a frozen embryo transfer rather than a fresh transfer. As a result, there
is no longer any difference between agonists and antagonists as far as pregnancy rates.
Antagonists however have proven to be more popular because the stimulation goes faster, there are
less injections to take and we don’t have that annoying problem of cysts forming in the ovaries.
This episode is part of a 3 part series on IV injections. Check out this playlist for all the
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