GnRH Agonists

GnRH Agonists are hormone-based fertility supplements which boost fertility either as a treatment for endometriosis, or in combination with ovulation-inducing drugs and assisted reproductive technologies such as IVF. GnRH stands for Gonadotropin Releasing Hormone. GnRH agonists have a similar effect to GnRH antagonists; however these are two different types of medical fertility supplements which work in slightly different ways.

Agonists In Women

GnRH agonists for women are available under many different brand names, one of which is Lupron. These fertility drugs mimic the function of Gonadotropin Releasing Hormone which is naturally produced in the body. GnRH agonists work on the part of the brain called the hypothalamus. They prevent the hypothalamus from sending signals to another part of the brain called the pituitary gland, telling the pituitary gland to produce sex hormones (gonadotropins) known as Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH), and estrogen. The effect is to block estrogen production and lower estrogen levels in the woman’s body, effectively inducing an artificial (and temporary) state of menopause. Bizarrely, this artificial state of menopause may help an infertile woman in the long term (if she suffers from endometriosis) or in the short term, if she is undergoing fertility treatment with In-Vitro Fertilization (IVF).

Agonists And Endometriosis

Endometriosis is a disorder of the female reproductive system in which excess endometrial tissue grows inside the uterus or even outside the uterus in other parts of the body. The endometrial tissue feeds on the female sex hormone estrogen. Endometriosis can cause infertility if the excess tissue causes scarring, blockages or distortion of the reproductive organs. This can reduce a woman’s ability to get pregnant if, for example, the fallopian tubes are twisted out of position and can no longer receive an egg from the ovaries.

By reducing estrogen levels in the body, GnRH agonists starve the endometrial tissue and cause it to shrink. In some cases, this may help the reproductive organs to regain their normal, healthy function and allow the woman to get pregnant after the treatment is stopped.

Although pregnancy is very unlikely during this treatment, a woman should not try to get pregnant while she is taking GnRH agonists, because these drugs can cause miscarriage or developmental problems in the fetus. Therefore, women taking GnRH agonists for endometriosis should use non-hormonal contraception for the duration of their treatment. Unfortunately, endometriosis tends to return after GnRH agonist treatment is stopped. This is one reason why GnRH agonists are not a guaranteed solution for fertility problems caused by endometriosis.

Agonists And IVF

During IVF treatment, GnRH agonists are often prescribed alongside ovulation-inducing drugs such as clomiphene. This may seem strange, given that GnRH agonists reduce the body’s levels of FSH, LH and estrogen hormones, all of which are necessary for ovulation and conception. Drugs such as clomiphene are prescribed precisely because they stimulate the production of these hormones in women who are no longer ovulating – so wouldn’t the GnRH agonists and the clomiphene just cancel each other out? Surely an artificial state of menopause is not going to be helpful during IVF?

The fact is that the GnRH agonists do not cancel out the clomiphene; rather, they regulate and control the clomiphene’s effects. Clomiphene increases FSH levels which stimulate the growth of follicles in the ovaries and encourages the follicles to produce eggs. The GnRH agonists prevent a premature surge in LH, brought about by the clomiphene, which could cause immature, poor quality eggs to be released by the ovaries. In IVF, it’s very important for the fertility specialist to be able to control the timing of the release of eggs, so that the eggs can be removed from the woman’s body for fertilization in the laboratory. The fertility specialist also wants to give the woman the best possible chance of a successful pregnancy, which is why the maturity and quality of her eggs is important too.

Injections And Sprays

GnRH agonists can be administered in three-monthly, monthly or daily injections, or via a nasal spray. The treating fertility specialist will decide on the best way of administering the fertility supplements to his or her patient.

Side Effects

As is the case with all medical fertility supplements, treatment with GnRH agonists brings with it the risk of certain side effects. These include:

- menopausal symptoms (hot flashes and all the rest)

- bone thinning (associated with low estrogen levels)

- irritation of the nose (when using a nasal spray form of the drugs)

- irritation of the injection site (when receiving an injectable form of the drugs)

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