Therapeutic use of gonadotropin-releasing hormone agonists in polycystic ovarian syndrome

Gonadotropin-Releasing Hormone (GnRH)/GnRH Receptors and Their Role in the Treatment of Endometriosis

Endometriosis, defined as the development of endometrial tissue outside of the uterine cavity, is a common gynecological disorder. The prevalence of pelvic endometriosis approaches 6%-10% in the general female population, and in women with pain, infertility, or both, the frequency is 35%-50%. The gold standard recommended process for diagnosing endometriosis is laparoscopy, an invasive surgical procedure, with or without histologic verification. The currently available nonsurgical treatments include oral contraceptives (estrogen-progestogen preparations), progestogen preparations (containing progesterone derivatives), androgenic hormones (danazol), and gonadotropin-releasing hormone (GnRH) agonists and antagonists. Two GnRH types have been discovered in mammals, GnRH I and GnRH II. In particular, GnRH I is released by the hypothalamus; however, it can be present in various tissues and organs of the body, including neural tissue, where it exerts neuroendocrine, autocrine, and paracrine actions in the peripheral and central nervous system (CNS). Interestingly, another GnRH isoform, GnRH III, has been identified, which has 60% similarity with GnRH I from which it varies by four amino acids. This peptide has been shown to have a significant role in reproduction, specifically in gametogenesis and steroidogenesis. Further research is needed to identify innovative treatment options for endometriosis, such as the therapeutic exogenous administration of GnRH II or antagonists of the GnRH I receptor. In this review, we examined the role of GnRH in endometriosis, outlining the specific actions of GnRH and GnRH receptors (GnRHRs). The innovative use of GnRH analogs and antagonists in the treatment of endometriosis is also discussed.

Triptorelin for the treatment of endometriosis

INTRODUCTION

Over the past 30 years, gonadotropin-releasing hormone agonists (GnRH-a) have been used to induce a hypoestrogenic status in women with endometriosis with the aim to cause an improvement in pain symptoms similar to that observed after menopause. Triptorelin is one of the most commonly used GnRH-a.

AREAS COVERED

This review offers an explanation of the mechanism of action, of the pharmacokinetics and pharmacodynamics of triptorelin and gives the readers a complete overview of the studies on the clinical efficacy, tolerability and safety of this agent in patients with endometriosis.

EXPERT OPINION

The studies reviewed in the current manuscript demonstrate the efficacy of triptorelin in improving pain symptoms caused by endometriosis. Further, this effect is confirmed by the reduction in the volume of the endometriotic nodules during treatment. Future research should evaluate whether the pre-operative administration of triptorelin prior to surgical excision of endometriomas may be useful in preserving the ovarian reserve.

Gonadotropin-releasing hormone analogs: Understanding advantages and limitations

Pituitary stimulation with pulsatile gonadotropin-releasing hormone (GnRH) analogs induces both follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Pituitary gonadotropin secretions are blocked upon desensitization when a continuous GnRH stimulus is provided by means of an agonist or when the pituitary receptors are occupied with a competitive antagonist. GnRH antagonists were not available originally; therefore, prolonged daily injections of agonist with its desensitizing effect were used. Today, single- and multiple-dose injectable antagonists are also available to block the LH surge and thus to cause desensitization. This review provides an overview of the use of GnRH analogs which is potent therapeutic agents that are considerably useful in a variety of clinical indications from the past to the future with some limitations. These indications include management of endometriosis, uterine leiomyomas, hirsutism, dysfunctional uterine bleeding, premenstrual syndrome, assisted reproduction, and some hormone-dependent tumours, other than ovulation induction.

Gonadotropin releasing hormone agonists: Expanding vistas

Gonadotropin-releasing hormone (GnRH) agonists are derived from native GnRH by amino acid substitution which yields the agonist resistant to degradation and increases its half-life. The hypogonadotropic hypogonadal state produced by GnRH agonists has been often dubbed as "pseudomenopause" or "medical oophorectomy," which are both misnomers. GnRH analogues (GnRH-a) work by temporarily "switching off" the ovaries. Ovaries can be "switched off" for the therapy and therapeutic trial of many conditions which include but are not limited to subfertility, endometriosis, adenomyosis, uterine leiomyomas, precocious puberty, premenstrual dysphoric disorder, chronic pelvic pain, or the prevention of menstrual bleeding in special clinical situations. Rapidly expanding vistas of usage of GnRH agonists encompass use in sex reassignment of male to female transsexuals, management of final height in cases of congenital adrenal hyperplasia, and preserving ovarian function in women undergoing cytotoxic chemotherapy. Hypogonadic side effects caused by the use of GnRH agonists can be tackled with use of "add-back" therapy. Goserelin, leuprolide, and nafarelin are commonly used in clinical practice. GnRH-a have provided us a powerful therapeutic approach to the treatment of numerous conditions in reproductive medicine. Recent synthesis of GnRH antagonists with a better tolerability profile may open new avenues for both research and clinical applications. All stakeholders who are partners in women's healthcare need to join hands to spread awareness so that these drugs can be used to realize their full potential.

Recent advances in the treatment of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a complex and heterogeneous disorder that presents a challenge for clinical investigators. It is the most common endocrine disorder of reproductive-aged women, yet the optimal therapeutic approach is unknown because the pathophysiological and molecular basis of the syndrome is not fully understood. Currently, the treatment is targeted to the patient's primary complaint. Treatment strategies focus on the reduction of clinical manifestations of hyperandrogenism (e.g., hirsutism), restoration of regular menses and achieving pregnancy. Pharmacological agents available for the treatment of hirsutism include androgen suppressors and peripheral androgen blockers. Combined oral contraceptive pills are the most commonly used androgen suppressor and the treatment of choice for menstrual dysfunction in PCOS patients who do not desire pregnancy. The first-line treatment for infertility in PCOS is clomiphene-citrate, whereas parenteral gonadotropins are commonly used in clomiphene-resistant patients. The benefits of insulin-sensitising agents for PCOS patients have become increasingly clear over the last decade. Metabolic disturbances associated with PCOS appear to have important long-term health implications and require further attention. This review summarises the current and emerging therapeutic strategies for the management of PCOS.

Combined oral contraceptives and gonadotropin releasing hormone agonistic analogs in polycystic ovary syndrome: clinical and experimental studies

Polycystic ovary syndrome is a common endocrine disorder, presenting with menstrual irregularities, hirsutism, obesity, infertility and abnormal ovarian morphology. In addition, polycystic ovary syndrome is associated with a self-perpetuating imbalance involving the endocrine system and metabolic pathways, in which carbohydrates, lipids and growth factors are involved. Because of its chronicity, it is considered to be a substantial risk factor for atherogenesis and hormone-dependent neoplasia. The etiology and pathophysiology of the syndrome remain elusive. However, during the last decade, several clues have emerged from human and animal studies that may have significant repercussions in the treatment of polycystic ovary syndrome. Therapeutic maneuvers should be directed towards the dominant abnormalities present in individual patients with polycystic ovary syndrome. Gonadotropin releasing hormone (GnRH) agonists can directly affect the gonadotropin generator and secondary downstream derangements, whereas combined oral contraceptives (COCs) can modify hypothalamic as well as peripheral abnormalities. In view of the fact that GnRH agonistic analogs (GnRH-a) will induce hypoestrogenemia and its sequelae, the add-back strategy of estrogenic supplementation is recommended for preventive reasons and, as it transpires from some studies, for enhancement of GnRH-a effectiveness.