science

Gonadotropin-releasing hormone antagonist

Gonadotropin-releasing hormone antagonist is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Gonadotropin-releasing hormone antagonist rather than just read about it. In short: Gonadotropin-releasing hormone antagonists (GnRH antagonists) are a class of medications that antagonize the gonadotropin-releasing hormone receptor (GnRH receptor) and thus the action of gonadotropin-releasing hormone (GnRH). They are used in the treatment of prostate cancer, endometriosis, uterine fibroids, female infertility in assisted reproduction, and for other indications.

Key takeaways

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Connect Gonadotropin-releasing hormone antagonist to a quantity you can measure, compute or draw — that is where exam questions come from.
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Reference excerpt

Gonadotropin-releasing hormone antagonists (GnRH antagonists) are a class of medications that antagonize the gonadotropin-releasing hormone receptor (GnRH receptor) and thus the action of gonadotropin-releasing hormone (GnRH). They are used in the treatment of prostate cancer, endometriosis, uterine fibroids, female infertility in assisted reproduction, and for other indications. Some GnRH antagonists, such as cetrorelix, are similar in structure to natural GnRH (a hormone made by neurons in the hypothalamus) but have an antagonistic effect, while other GnRH antagonists, such as elagolix and relugolix, are non-peptide and small-molecule compounds. GnRH antagonists compete with natural GnRH for binding to GnRH receptors, thus decreasing or blocking GnRH action in the body.

Medical uses

Prostate cancer Testosterone promotes growth of many prostate tumors and therefore reducing circulating testosterone to very low (castration) levels is often the treatment goal in the management of men with advanced prostate cancer. GnRH antagonists are used to provide fast suppression of testosterone without the surge in testosterone levels that is seen when treating patients with GnRH agonists. In patients with advanced disease, this surge in testosterone can lead to a flare-up of the tumour, which can precipitate a range of clinical symptoms such as bone pain, urethral obstruction, and spinal cord compression. Drug agencies have issued warnings regarding this phenomenon in the prescribing information for GnRH agonists. As testosterone surge does not occur with GnRH antagonists, there is no need for patients to receive an antiandrogen as flare protection during prostate cancer treatment. GnRH agonists also induce an increase in testosterone levels after each reinjection of the drug – a phenomenon that does not occur with GnRH antagonists. The reduction in testosterone levels that occurs during GnRH antagonist therapy subsequently reduces the size of the prostate cancer. This in turn results in a reduction in prostate-specific antigen (PSA) levels in the patient's blood and so measuring PSA levels is a way to monitor how patients with prostate cancer are responding to treatment. GnRH antagonists have an immediate onset of action leading to a fast and profound suppression of testosterone and are therefore especially valuable in the treatment of patients with prostate cancer, where fast control of disease is needed. The GnRH antagonist abarelix was withdrawn from the United States market in 2005 and is now only marketed in Germany for use in patients with symptomatic prostate cancer. Degarelix is a GnRH antagonist that is approved for use in patients with advanced hormone-sensitive prostate cancer throughout Europe and also in the United States.

Fertility treatment

GnRH antagonists are also used for short periods in the prevention of premature LH surge and endogenous ovulation in patients undergoing ovarian hyperstimulation with FSH in preparation for in-vitro fertilization (IVF). Typically they are administered in the mid-follicular phase in stimulated cycles after administration of gonadotropins and prior to the administration of hCG – which is given to stimulate ovulation. This protocol is likely beneficial in women expected to be hyper-responders, and probably also those expected to be poor responders to ovarian hyperstimulation. There is probably little or no difference between GnRH antagonist and GnRH agonist protocols in terms of live birth or risk of miscarriage but GnRH antagonists probably reduce the risk of ovarian hyperstimulation syndrome. The GnRH antagonists that are currently licensed for use in fertility treatment are cetrorelix and ganirelix.

Uterine disorders Elagolix is indicated for the treatment of moderate to severe endometriosis pain and relugolix is indicated for the treatment of uterine fibroids.

Other uses GnRH antagonists are being investigated in the treatment of women with hormone-sensitive breast cancer. In men, they are being investigated in the treatment of benign prostatic hyperplasia and also as potential contraceptive agents. GnRH antagonists could be used as puberty blockers in transgender youth and to suppress sex hormone levels in transgender adolescents and adults.

Available forms

Currently approved GnRH antagonists include the peptide molecules abarelix, cetrorelix, degarelix, and ganirelix and the small-molecule compounds elagolix and relugolix. GnRH antagonists are administered by subcutaneous injection (cetrorelix, degarelix, ganirelix), by intramuscular injection (abarelix), or by oral administration (elagolix, relugolix). Another non-peptide and orally-active GnRH antagonist that is in development is linzagolix.

Side effects As with all hormonal therapies, GnRH antagonists are commonly associated with hormonal side effects such as hot flushes, headache, nausea and weight gain. When used in fertility treatment they can also be associated with abdominal pain and ovarian hyperstimulation. Subcutaneously administered agents are also associated with injection-site reactions and abarelix (neither of these being GnRH agonists, but instead being antagonists) has been linked with immediate-onset systemic allergic reactions.

Pharmacology GnRH antagonists competitively and reversibly bind to GnRH receptors in the pituitary gland, blocking the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary. In men, the reduction in LH subsequently leads to rapid suppression of testosterone production in the testes; in women it leads to suppression of estradiol and progesterone production from the ovaries. GnRH antagonists are able to abolish gonadal sex hormone production and to suppress sex hormone levels into the castrate range, or by approximately 95%. Unlike the GnRH agonists, which cause an initial stimulation of the hypothalamic–pituitary–gonadal axis (HPG axis) that leads to a surge in testosterone or estrogen levels, GnRH antagonists have an immediate onset of action and rapidly reduce sex hormone levels without an initial surge.

Chemistry GnRH antagonists include peptides such as cetrorelix and non-peptide and small-molecule compounds such as elagolix. Peptide GnRH antagonists are GnRH analogues.

See also Gonadotropin-releasing hormone modulator Gonadotropin-releasing hormone agonist

References

External links

Illustrations

Worked examples

Example 1 — a first encounter with Gonadotropin-releasing hormone antagonist

Start with the simplest possible case. Write down what Gonadotropin-releasing hormone antagonist claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Gonadotropin-releasing hormone antagonist before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Gonadotropin-releasing hormone antagonist ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Gonadotropin-releasing hormone antagonist

In research: Gonadotropin-releasing hormone antagonist appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Gonadotropin-releasing hormone antagonist in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Gonadotropin-releasing hormone antagonist is common in secondary-school and first-year university syllabi. It links to neighbouring topics Antiandrogens, Antigonadotropins, Gonadotropin-releasing hormone and gonadotropins, so understanding it makes those chapters shorter.
In everyday life: Look for Gonadotropin-releasing hormone antagonist outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Gonadotropin-releasing hormone antagonist in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gonadotropin-releasing hormone antagonist means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Gonadotropin-releasing hormone antagonist out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gonadotropin-releasing hormone antagonist in simple terms?

Why does Gonadotropin-releasing hormone antagonist matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Gonadotropin-releasing hormone antagonist?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Gonadotropin-releasing hormone antagonist.