What is the Difference Between GnRH Agonist and GnRH Antagonist

The key difference between GnRH agonist and GnRH antagonist is that GnRH agonist works by increasing or decreasing the release of gonadotropins and the production of sex hormones, while GnRH antagonist works by blocking GnRH action in the body, decreasing the release of gonadotropins and the production of sex hormones.

Everyone produces gonadotropin-releasing hormone (GnRH). In adolescence or in puberty, the increased levels of this hormone stimulate the production of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). This helps sex glands to mature and function properly. However, in some instances, GnRH medications are used to stop the pituitary gland from making the hormones that stimulate the production of sex hormones. This helps treat diseases like breast cancer, prostate cancer, infertility, etc. GnRH agonists and GnRH antagonists are two different types of GnRH medications.

CONTENTS

1. Overview and Key Difference
2. What is GnRH Agonist
3. What is GnRH Antagonist
4. Similarities – GnRH Agonist and GnRH Antagonist
5. GnRH Agonist vs GnRH Antagonist in Tabular Form
6. Summary – GnRH Agonist vs GnRH Antagonist

What is GnRH Agonist?

GnRH agonist is a GnRH medication that activates the pituitary gland to make more luteinizing hormone and FSH hormone. However, as time goes on, the pituitary gland stops responding to constant GnRH agonists and stops making both these hormones, thereby stopping the production of sex hormones. Therefore, GnRH agonist is a type of medication that affects gonadotropins and sex hormones in the body. GnRH agonist is useful in fertility medicine to lower sex hormone levels in the treatment of hormone-sensitive cancers like prostate cancer and breast cancer, for suppression of spontaneous ovulation as a part of infertility treatment, for certain gynecological disorders such as heavy periods, endometriosis, high testosterone levels in women, and early puberty in children, for the transgender hormone therapy, and delaying or blocking puberty in transgender youth. This is usually given by injections into fat, as implants placed into fat, or as nasal sprays.

The side effects of GnRH agonists may include symptoms of hypogonadism, which include hot flashes, gynecomastia, fatigue, weight gain, fluid retention, erectile dysfunction, and low level of libido. Furthermore, GnRH agonists that are available in the market for medical purposes include buserelin, gonadorelin, goserelin, histrelin, leuprorelin, nafarelin, and triptorelin.

What is GnRH Antagonist?

GnRH antagonist is a GnRH medication that directly prevents the pituitary gland from responding to GnRH hormone; thus, the pituitary gland stops making luteinizing hormones or sex hormones. It is a class of medication that antagonizes the gonadotropin-releasing hormone receptor (GnRH receptor). Therefore, it also antagonizes the action of gonadotropin-releasing hormone (GnRH). Moreover, it is used in the treatment of diseases such as prostate cancer, endometriosis, uterine fibroids, female infertility, and in assisted reproduction procedures. GnRH antagonist is given by subcutaneous injection, intramuscular injection, or by oral administration.

GnRH antagonist is involved with side effects like hot flashes, headache, nausea, weight gain, abdominal pain, ovarian hyperstimulation, injection-site reactions, and immediate-onset systemic allergic reactions. Furthermore, examples of GnRH antagonists currently available on the market include abarelix, cetrorelix, degarelix, ganirelix, elagolix, and relugolix.

What are the Similarities Between GnRH Agonist and GnRH Antagonist?

• GnRH agonists and GnRH antagonists are two different types of GnRH medications.
• Both have been available for medical use since the 1980s.
• They can reduce the level of gonadotropins and sex hormones.
• Both are currently used for the treatment of different diseases.
• Usage of both has different side effects.

What is the Difference Between GnRH Agonist and GnRH Antagonist?

GnRH agonist is an agonist of the GnRH receptor that works by increasing or decreasing the release of gonadotropins and the production of sex hormones, while GnRH antagonist is an antagonist of the gonadotropin-releasing hormone receptor (GnRH receptor) that works by blocking GnRH action in the body, decreasing the release of gonadotropins and the production of sex hormones. Thus, this is the key difference between GnRH agonist and GnRH antagonist. Furthermore, some GnRH agonists available for medical use in the market are buserelin, gonadorelin, goserelin, histrelin, leuprorelin, nafarelin, and triptorelin. On the other hand, some GnRH antagonists available for medical use in the market are abarelix, cetrorelix, degarelix, ganirelix, elagolix, and relugolix.

The following table summarizes the difference between GnRH agonist and GnRH antagonist.

Summary – GnRH Agonist vs. GnRH Antagonist

Gonadotropin hormone-releasing hormone (GnRH) is the key element that determines the secretion of gonadotropins, such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Both regulate the endocrine function and gamete maturation in the sex glands. GnRH medications affect GnRH and GnRH receptors and can stop the pituitary gland from making the hormones (FSH and LH) that stimulate the production of sex hormones. GnRH medications are particularly very important in treating some diseases. GnRH agonists and GnRH antagonists are two different types of GnRH medications. GnRH agonist is an agonist of the GnRH receptor and works by increasing or decreasing the release of gonadotropins and the production of sex hormones, while GnRH antagonist is an antagonist of the gonadotropin-releasing hormone receptor (GnRH receptor) and works by blocking GnRH action in the body, decreasing the release of gonadotropins and the production of sex hormones. This summarizes the difference between GnRH agonist and GnRH antagonists.

Reference:

1. Tomabal, Bertrand, et al. “GnRH Antagonist: A New and an Effective Way of Treatment of Advanced Prostate Cancer.” Indian Journal of Surgical Oncology.
2. “Gonadotropin Releasing Hormone (Gnrh) Analogues.” LiverTox – NCBI Bookshelf.

Image Courtesy:

1. “Linzagolix molecule ball” By Medgirl131 – This image was created with Discovery Studio Visualizer. (CC0) via Commons Wikimedia
2. “Testosterone levels in men with prostate cancer treated with GnRH agonists and antagonists” By AmazingCosima – Own work (CC BY-SA 4.0) via Commons Wikimedia