What is a short protocol with gnrh antagonists?

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GnRH antagonists are drugs that are used in assisted reproduction treatments to control ovarian function and prevent spontaneous ovulation. They are the agonists of GnRH most used in short protocols of ovarian stimulation. We can find them with different chemical compositions and commercial names, but their function is the same, whether they are used in treatments with artificial insemination or in in vitro fertilization (IVF).

Below you have an index with all the points that we will discuss in this article.

Index

What is a short protocol with GnRH antagonists?

What are GnRH antagonists?

GnRH antagonists are drugs belonging to the group of gonadotropin-releasing hormone (GnRH) analogs, which are used in the ovarian stimulation of assisted reproduction treatments (artificial insemination, in vitro fertilization and ICSI). Thanks to them, we can control the ovarian function.

The purpose of these hormones is to avoid the LH peak, which would cause ovulation and early follicular luteinization. In this way, we can control the moment in which this occurs so that it does not occur prematurely.

If there was a spontaneous ovulation, it would not be possible to recover the ovules in the follicular puncture or to perform artificial insemination on the optimal day for fertilization to occur.

Mechanism of action of GnRH antagonists

In addition, the LH peak would also affect endometrial receptivity. Therefore, in women who require endometrial preparation, either to transfer frozen embryos or for ovodonation treatments, GnRH analogs are also administered.

It should be noted that its use is not exclusive to assisted reproduction patients: they are also indicated, for example, in the treatment of endometriosis and hormone-dependent tumors, such as breast or prostate cancer.

Effects: how does it act?

Once a GnRH antagonist is administered, it binds to the GnRH receptors and blocks them. In this way, it prevents the GnRH from joining its receptors through a competitive blockade. These receptors are located on the surface of the gonadotrophic cells of the pituitary gland.

By blocking the GnRH receptors, in turn, the synthesis of gonadotrophins (FSH and LH) by the pituitary gland is inhibited. These hormones exert their function in the ovary: they are involved in the regulation of the menstrual cycle. Therefore, GnRH antagonists slow ovarian activity and inhibit the menstrual cycle.

Unlike what happens with the GnRH agonists, its action is immediate and does not produce a flare-up effect, which means that, at the beginning of administering the agonists, the segregation of FSH and LH increases.

The immediacy of its action and the absence of flare-up effect make it necessary, in comparison with the protocols with GnRH agonists, to inject less doses of antagonists to achieve the same hypophyseal suppression. Therefore, it simplifies ovarian stimulation and makes it less bothersome for the patient: we spend approximately one month of hormonal treatment at 10-12 days.

Comparison of the effect of agonists and antagonists

Advantages: simplification of treatments

The benefits of using this drug in ovarian stimulation treatments are the following:

  • Immediate suppression of serum LH levels occurs and prevents premature ovulation. Because their effect is so rapid, they can be administered at a time when there is a clear risk that the LH surge will occur, since it takes hours to achieve pituitary inhibition. In the case of agonists, they need 7-10 days to achieve this effect.
  • The duration of ovulation stimulation treatment is shorter, so that discomfort to patients is reduced: fewer injections are needed and they must go to the office less often to perform controls during ovarian stimulation.
  • It is usually well tolerated by women, with few side effects, since the stimulation is not very aggressive because it allows to administer lower doses of FSH. The fact that less hormones are needed also makes the treatment cheaper.
  • It decreases the frequency of ovarian hyperstimulation syndrome (OHSS) because it allows GnRH agonists to be used to induce ovulation instead of hCG, which increases the risk of OHSS. Therefore, these protocols are especially indicated in patients with an elevated risk of OHSS: young women, such as donors, or with polycystic ovarian syndrome.
  • It does not cause follicular cysts because it does not have the flare-up effect that originates after the administration of GnRH agonists.

For all these reasons, short protocols with GnRH antagonists are increasingly used among specialists in assisted reproduction. The most used GnRH antagonists in these treatments are Cetrotide (cetrorelix) and Orgalutran (ganirelix).

Disadvantages

The use of GnRH antagonists presents few drawbacks since, being a stimulation not too aggressive, it is tolerated by most women without practically contraindications.

The only problem that exists is that, in many studies, the pregnancy rate has turned out to be slightly lower (between 3% and 5% lower) than that obtained in ovarian stimulation protocols in which GnRH analogues are used. This is due to the effect that antagonists have on endometrial receptivity.

In addition, if oral contraceptives or estrogen are not administered before initiating treatment with antagonists, it may cause asynchrony in follicular growth, which also negatively affects success rates because fewer ovules are recovered per cycle.

Questions from users

For ovarian stimulation, is it enough to inject GnRH antagonists?

No. GnRH antagonists only serve to control endogenous hormone levels. It is necessary to stimulate follicular growth with the administration of gonadotropins and induce ovulation by hCG or GnRH agonists.

How many days does ovarian stimulation last with GnRH antagonists?

With the use of GnRH antagonists, the duration of ovarian stimulation is approximately 10-12 days. It will depend on the exact protocol used and the woman's response to hormone treatment.

Recommended reading

If you want to know more about the drugs used in ovarian stimulation treatments, you will find more information in this article: Drugs used in controlled ovarian stimulation.

On the other hand, if you want to know the price of these drugs, we recommend that you access the following link: Prices of hormonal medication in assisted reproduction.

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