Gonadotropin-releasing hormone analogue

Gonadotropin-releasing hormone analogue
	Drug class
	GnRH, the peptide hormone from which all GnRH analogues are derived.
Class identifiers
Synonyms	GnRH blockers; GnRH inhibitors; Antigonadotropins
Use	Infertility; Prostate cancer; Precocious puberty; Breast cancer; Endometriosis; Uterine fibroids; Transgender people
Biological target	GnRH receptor
Chemical class	Peptides
	In Wikidata

Last updated April 04, 2019

A gonadotropin-releasing hormone analogue (GnRH analogue or analog), also known as a luteinizing hormone releasing hormone agonist (LHRH agonist) or LHRH analogue is a synthetic peptide drug modeled after the human hypothalamic gonadotropin-releasing hormone (GnRH). A GnRH analogue is designed to interact with the GnRH receptor and modify the release of the pituitary gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) for therapeutic purposes. Shortly after the discovery of GnRH by Nobel laureates Guillemin and Schally, researchers tried to modify the GnRH decapeptide with the intent to create analogues that could activate or block the receptor. Examples include goserelin and leuprorelin.^[1]

Peptides are short chains of amino acid monomers linked by peptide (amide) bonds.

Medication substance used to diagnose, cure, treat, or prevent disease

A medication is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and relies on the science of pharmacology for continual advancement and on pharmacy for appropriate management.

The hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus is located below the thalamus and is part of the limbic system. In the terminology of neuroanatomy, it forms the ventral part of the diencephalon. All vertebrate brains contain a hypothalamus. In humans, it is the size of an almond. The hypothalamus is responsible for the regulation of certain metabolic processes and other activities of the autonomic nervous system. It synthesizes and secretes certain neurohormones, called releasing hormones or hypothalamic hormones, and these in turn stimulate or inhibit the secretion of hormones from the pituitary gland. The hypothalamus controls body temperature, hunger, important aspects of parenting and attachment behaviours, thirst, fatigue, sleep, and circadian rhythms. The hypothalamus derives its name from Greek ὑπό, under and θάλαμος, chamber.

Elagolix, sold under the brand name Orilissa, is a gonadotropin-releasing hormone antagonist medication which is used in the treatment of pain associated with endometriosis in women. It is also under development for the treatment of uterine fibroids and heavy menstrual bleeding in women. The medication was under investigation for the treatment of prostate cancer and enlarged prostate in men as well, but development for these conditions was discontinued. Elagolix is taken by mouth once or twice per day. It can be taken for up to 6 to 24 months, depending on the dosage.

Relugolix, sold under the brand name Relumina, is a gonadotropin-releasing hormone antagonist medication which is used in the treatment of uterine fibroids in Japan. It is also under development for use in other countries and for the additional indications of endometriosis and prostate cancer. Unlike most other GnRH modulators, but similarly to elagolix, relugolix is a non-peptide and small-molecule compound and is orally active. As of February 2019, it is in phase III clinical trials for endometriosis and prostate cancer. The medication was approved for use for the treatment of uterine fibroids in Japan in January 2019. A New Drug Application of relugolix for uterine fibroids is expected to be submitted in the United States late 2019.

Oral administration is a route of administration where a substance is taken through the mouth. Per os (P.O.) is sometimes used as an abbreviation for medication to be taken orally. Many medications are taken orally because they are intended to have a systemic effect, reaching different parts of the body via the bloodstream, for example.

Agonists

A gonadotropin-releasing hormone agonist (GnRH agonist) is an analogue that activates the GnRH receptor resulting in increased secretion of FSH and LH. Initially it was thought that agonists could be used as potent and prolonged stimulators of pituitary gonadotropin release, but it was soon recognized that agonists, after their initial stimulating action – termed a “flare” effect - eventually caused a paradoxical and sustained drop in gonadotropin secretion. This second effect was termed “downregulation” and can be observed after about 10 days. While this phase is reversible upon stopping the medication, it can be maintained when GnRH agonists use is continued for a long time.

Antagonists

A gonadotropin-releasing hormone antagonist (GnRH antagonist) is an analogue that blocks the GnRH receptor resulting in an immediate drop in gonadotropin (FSH, LH) secretion. The GnRH antagonist is primarily used in IVF treatments to block natural ovulation.

All GnRH analogues are contraindicated in pregnancy (pregnancy category X).

The pregnancy category of a medication is an assessment of the risk of fetal injury due to the pharmaceutical, if it is used as directed by the mother during pregnancy. It does not include any risks conferred by pharmaceutical agents or their metabolites in breast milk.

Related Research Articles

Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. In females, an acute rise of LH triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell–stimulating hormone (ICSH), it stimulates Leydig cell production of testosterone. It acts synergistically with FSH.

Follicle-stimulating hormone (FSH) is a gonadotropin, a glycoprotein polypeptide hormone. FSH is synthesized and secreted by the gonadotropic cells of the anterior pituitary gland, and regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and luteinizing hormone (LH) work together in the reproductive system.

Gonadotropin-releasing hormone (GnRH) is a releasing hormone responsible for the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. GnRH is a tropic peptide hormone synthesized and released from GnRH neurons within the hypothalamus. The peptide belongs to gonadotropin-releasing hormone family. It constitutes the initial step in the hypothalamic–pituitary–gonadal axis.

Gonadotropins are glycoprotein polypeptide hormones secreted by gonadotrope cells of the anterior pituitary of vertebrates. This family includes the mammalian hormones follicle-stimulating hormone (FSH), luteinizing hormone (LH), and placental/chorionic gonadotropins, human chorionic gonadotropin (hCG) and equine chorionic gonadotropin (eCG), as well as at least two forms of fish gonadotropins. These hormones are central to the complex endocrine system that regulates normal growth, sexual development, and reproductive function. LH and FSH are secreted by the anterior pituitary gland, while hCG and eCG are secreted by the placenta in pregnant humans and mares, respectively. The gonadotropins act on the gonads, controlling gamete and sex hormone production.

Fertility medication, better known as fertility drugs, are drugs which enhance reproductive fertility. For women, fertility medication is used to stimulate follicle development of the ovary. There are currently very few fertility medication options available for men.

Gonadorelin is a gonadotropin-releasing hormone agonist which is used in fertility medicine and to treat amenorrhea and hypogonadism. It is also used in veterinary medicine. The medication is a form of the endogenous GnRH and is identical to it in chemical structure. It is given by injection into a blood vessel or fat or as a nasal spray.

Triptorelin, sold under the brand names Decapeptyl and Gonapeptyl among others, is a medication that causes stimulation of the pituitary, thus decreasing secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

A gonadotropin-releasing hormone agonist is a type of medication which affects gonadotropins and sex hormones. They are used for a variety of indications including in fertility medicine and to lower sex hormone levels in the treatment of hormone-sensitive cancers such as prostate cancer and breast cancer, certain gynecological disorders like heavy periods and endometriosis, high testosterone levels in women, early puberty in children, as a part of transgender hormone therapy, and to delay puberty in transgender youth among other uses. GnRH agonists are given by injections into fat, as implants placed into fat, and as nasal sprays.

Gonadotropin-releasing hormone antagonists are a class of medications that antagonize the gonadotropin-releasing hormone 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.

The gonadotropin-releasing hormone receptor (GnRHR), also known as the luteinizing hormone releasing hormone receptor (LHRHR), is a member of the seven-transmembrane, G-protein coupled receptor (GPCR) family. It is the receptor of gonadotropin-releasing hormone (GnRH). The GnRHR is expressed on the surface of pituitary gonadotrope cells as well as lymphocytes, breast, ovary, and prostate.

Kisspeptin is a protein that is encoded by the KISS1 gene in humans. Kisspeptin is a G-protein coupled receptor ligand for GPR54. Kiss1 was originally identified as a human metastasis suppressor gene that has the ability to suppress melanoma and breast cancer metastasis. Kisspeptin-GPR54 signaling has an important role in initiating secretion of gonadotropin-releasing hormone (GnRH) at puberty, the extent of which is an area of ongoing research. Gonadotropin-releasing hormone is released from the hypothalamus to act on the anterior pituitary triggering the release of luteinizing hormone (LH), and follicle stimulating hormone (FSH). These gonadotropic hormones lead to sexual maturation and gametogenesis. Disrupting GPR54 signaling can cause hypogonadotrophic hypogonadism in rodents and humans. The Kiss1 gene is located on chromosome 1. It is transcribed in the brain, adrenal gland, and pancreas.

Histrelin acetate, sold under the brand names Vantas and Supprelin LA among others, is a nonapeptide analogue of gonadotropin-releasing hormone (GnRH) with added potency. When present in the bloodstream, it acts on particular cells of the pituitary gland called gonadotropes. Histrelin stimulates these cells to release luteinizing hormone and follicle-stimulating hormone. Thus it is considered a gonadotropin-releasing hormone agonist or GnRH agonist.

Cetrorelix, or cetrorelix acetate, sold under the brand name Cetrotide, is an injectable gonadotropin-releasing hormone (GnRH) antagonist. A synthetic decapeptide, it is used in assisted reproduction to inhibit premature luteinizing hormone surges The drug works by blocking the action of GnRH upon the pituitary, thus rapidly suppressing the production and action of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In addition, cetrorelix can be used to treat hormone-sensitive cancers of the prostate and breast and some benign gynaecological disorders. It is administered as either multiple 0.25 mg daily subcutaneous injections or as a single-dose 3 mg subcutaneous injection. The duration of the 3 mg single dose is four days; if human chorionic gonadotropin (hCG) is not administered within four days, a daily 0.25 mg dose is started and continued until hCG is administered.

Controlled ovarian hyperstimulation is a technique used in assisted reproduction involving the use of fertility medications to induce ovulation by multiple ovarian follicles. These multiple follicles can be taken out by oocyte retrieval for use in in vitro fertilisation (IVF), or be given time to ovulate, resulting in superovulation which is the ovulation of a larger-than-normal number of eggs, generally in the sense of at least two. When ovulated follicles are fertilised in vivo, whether by natural or artificial insemination, there is a very high risk of a multiple pregnancy.

Degarelix (INN) or degarelix acetate (USAN), sold under the brand name Firmagon among others, is a hormonal therapy used in the treatment of prostate cancer.

Hypogonadotropic Hypogonadism (HH), is due to problems with either the hypothalamus or pituitary gland affecting the hypothalamic-pituitary-gonadal axis. Hypothalamic disorders results from a deficiency in the release of gonadotropic releasing hormone (GnRH), while pituitary gland disorders are due to a deficiency in the release of gonadotropins from the anterior pituitary. GnRH is the central regulator in reproductive function and sexual development via the HPG axis. GnRH is released by hypothalamic neuroendocrine cells into the hypophyseal portal system acting on gonadotrophs in the anterior pituitary. The release of gonadotropins, LH and FSH, act on the gonads for the development and maintenance of proper adult reproductive physiology. LH acts on Leydig cells in the male testes and theca cells in the female. FSH acts on Sertoli cells in the male and follicular cells in the female. Combined this causes the secretion of gonadal sex steroids and the initiation of folliculogenesis and spermatogenesis. The production of sex steroids forms a negative feedback loop acting on both the anterior pituitary and hypothalamus causing a pulsatile secretion of GnRH. GnRH neurons lack sex steroid receptors and mediators such as kisspeptin stimulate GnRH neurons for pulsatile secretion of GnRH.

The gonadotropin receptors are a group of receptors that bind a group of pituitary hormones called gonadotropins. They include the:

Fezolinetant (INN; former developmental code name ESN-364) is a small-molecule, orally active, selective neurokinin-3 (NK₃) receptor antagonist which is under development by Ogeda (formerly Euroscreen) for the treatment of sex hormone-related disorders. As of May 2017, it has completed phase I and phase IIa clinical trials for hot flashes in postmenopausal women. Phase IIa trials in polycystic ovary syndrome patients are ongoing. In April 2017, it was announced that Ogeda would be acquired by Astellas Pharma.

References

↑ Speroff L, Glass RH, Kase NG. Clinical Gynecologic Endocrinology and Infertility. Fifth Edition. Willimas 7 Wilkins, Baltimore. 1994. Pages 160-161.

External links

History of GnRH agonist and antagonist development

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[1] Speroff L, Glass RH, Kase NG. Clinical Gynecologic Endocrinology and Infertility. Fifth Edition. Willimas 7 Wilkins, Baltimore. 1994. Pages 160-161.