The role of LHRH agonists and antagonists

A comparison of aerobic- and resistance-emphasised exercise on cardiometabolic health and quality of life in men receiving androgen deprivation therapy for prostate cancer: Protocol for a feasibility trial

BACKGROUND

Those with intermediate and high-risk prostate cancer typically receive androgen deprivation therapy (ADT) as part of their treatment. ADT often results in extensive side effects including increased risk of cardiometabolic disease. Many ADT side effects can be influenced by exercise, both resistance and aerobic training. Exercise regimes typically combine aerobic and resistance exercise but the appropriate emphasis for achieving the broadest range of therapeutic benefits has yet to be determined. We propose to determine the feasibility of undertaking a larger trial comparing a resistance- vs an aerobic-emphasised exercise intervention in men with prostate cancer undergoing ADT. The trial will also investigate preliminary evidence of difference between arms for cardiometabolic health and quality of life outcomes.

METHODS

This is a 6-month randomised two-armed feasibility trial. Prostate cancer patients undergoing ADT and radiotherapy will be recruited (n = 24) and randomised to either a resistance- or aerobic-emphasised group. Participants will attend twice-weekly supervised individual or small group sessions, with 75% of exercise time in the primary exercise modality. The primary outcome will be feasibility, determined via assessment of recruitment, retention, adherence, safety, and acceptability. Secondary outcomes will include quality of life, body composition, vascular indices, aerobic and muscular fitness and cardiometabolic health blood biomarkers.

CONCLUSION

It is envisaged that the trial will provide valuable information and preliminary difference data that will aid in the design of an efficacious larger trial that will adopt a major and minor emphasis approach to the scheduling of resistance and aerobic exercise.

Overview of elagolix for the treatment of endometriosis

INTRODUCTION

Suppression of sex-steroid secretion is required in a variety of gynecological conditions. This can be achieved using gonadotropin releasing hormone (GnRH) agonists that bind pituitary gonadotropin receptors and antagonize the link-receptor of endogenous GnRH, inhibiting the mechanism of GnRH pulsatility. On the other hand, GnRH antagonists immediately reduce gonadal steroid levels, avoiding the initial stimulatory phase of the agonists. Potential benefits of GnRH antagonists over GnRH agonists include a rapid onset and reversibility of action. Older GnRH antagonists are synthetic peptides, obtained by modifications of certain amino acids in the native GnRH sequence. They require subcutaneous injections, implantation of long-acting depots. The peptide structure is responsible for histamine-related adverse events and the tendency to elicit hypersensitivity reactions.

AREAS COVERED

Research has worked towards the development of non-peptidic molecules exerting antagonist action on GnRH. They are available for oral administration and may have a more beneficial safety profile in comparison with peptide GnRH antagonists. This article focuses on the data of the literature about elagolix, a novel non-peptidic GnRHantagonist, in the treatment of endometriosis.

EXPERT OPINION

Elagolix demonstrated efficacy in the management of endometriosis-associated pain and had an acceptable safety and tolerability profile. However, further studies are necessary to evaluate its non-inferiority in comparison with other endometriosis's treatments.

Gonadotrophin-releasing hormone (GnRH) and GnRH agonists: mechanisms of action

The hypothalamic decapeptide gonadotrophin-releasing hormone (GnRH) binds to specific receptors on pituitary gonadotrophs. These receptors belong to the family of G protein-coupled receptors. Their activation leads to phosphoinositide breakdown with generation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) and diacylglycerol. These second messengers initiate Ca2+ release from intracellular stores and activation of protein kinase C, both of which are important for gonadotrophin secretion and synthesis. Prolonged activation of GnRH receptors by GnRH leads to desensitization and consequently to suppressed gonadotrophin secretion. This is the primary mechanism of action of agonistic GnRH analogues. By contrast, GnRH antagonists compete with GnRH for receptors on gonadotroph cell membranes, inhibit GnRH-induced signal transduction and consequently gonadotrophin secretion. These compounds are free of agonistic actions, which might be beneficial in certain clinical applications.

Ovarian stimulation: from basic science to clinical application

Treatment for infertility, including ovarian stimulation, was first introduced almost 100 years ago. At this time, radiation therapy became an established treatment, and it was only some decades later that the problem of radiation-induced cancer emerged. Non-human gonadotrophins, such as pregnant mare serum gonadotrophin (PMSG), and human pituitary gonadotrophins (HPG), were commonly used for hormonal stimulation procedures. However, use of PMSG led to antibody formation, and it was therefore only useful for the first treatment cycle. HPG produced good results, but its use came to an end in the late 1980s when it was linked to the development of Creutzfeldt-Jakob disease. The first hormonal product from human menopausal urine to be used was human menopausal gonadotrophin (HMG), followed later by purified preparations of this product. All of these preparations contained a high percentage of unknown urinary proteins, which interfered with batch-to-batch consistency. This changed with the introduction of recombinant gonadotrophins, produced from an immortalized/standardized mammalian cell line (CHO). More recent developments include the introduction of long-acting gonadotrophin formulations. The development of gonadotrophin-releasing hormone (GnRH) analogues and more recently the use of GnRH antagonists has helped to improve ovarian stimulation protocols by optimizing their efficacy, and making them easier to administer.

GnRH antagonists: do they open new pathways to safer treatment in assisted reproductive techniques?

GnRH antagonists (GnRHnt) induce a rapid decrease in LH and FSH, preventing and interrupting LH surges. Their properties do not require a desensitization period and allow their use in the late follicular phase. GnRHnt could replace GnRH agonists (GnRHa) in ovarian stimulation without their side-effects and their long period of desensitivity. Both protocols using GnRHnt were associated with a smaller amount of gonadotrophin, a shorter stimulation period and a lower incidence of ovarian hyperstimulation syndrome (OHSS) with statistically comparable pregnancy rates. There is room for improvement of both protocols concerning the programming, the antagonist dose and the timing of antagonist administration. Luteal support should be maintained until the results of further studies. The perinatal outcome appears to be similar to that of other stimulation regimens. Triggering of ovulation can be facilitated by GnRHa for patients at risk of OHSS. Provided that pregnancy rates equivalent to those obtained with GnRHa are confirmed in larger series, GnRHnt will clearly represent a safer alternative to GnRHa protocols in IVF.

Ovarian stimulation: from basic science to clinical application

Treatment for infertility, including ovarian stimulation, was first introduced almost 100 years ago. At this time, radiation therapy became an established treatment, and it was only some decades later that the problem of radiation-induced cancer emerged. Non-human gonadotrophins, such as pregnant mare serum gonadotrophin (PMSG), and human pituitary gonadotrophins (HPG), were commonly used for hormonal stimulation procedures. However, use of PMSG led to antibody formation, and it was therefore only useful for the first treatment cycle. HPG produced good results, but its use came to an end in the late 1980s when it was linked to the development of Creutzfeldt-Jakob disease. The first hormonal product from human menopausal urine to be used was human menopausal gonadotrophin (HMG), followed later by purified preparations of this product. All of these preparations contained a high percentage of unknown urinary proteins, which interfered with batch-to-batch consistency. This changed with the introduction of recombinant gonadotrophins, produced from an immortalized/standardized mammalian cell line (CHO). More recent developments include the introduction of long-acting gonadotrophin formulations. The development of gonadotrophin-releasing hormone (GnRH) analogues and more recently the use of GnRH antagonists has helped to improve ovarian stimulation protocols by optimizing their efficacy, and making them easier to administer.

Unmet therapeutic needs for uterine myomas

Uterine myomas may develop in many women, but only become clinically significant in about one third of the affected population. Although uterine myomas are most often benign, they are associated with debilitating symptoms and commonly result in hysterectomy. Current treatments for uterine myomas include pharmacologic therapies, delivery of focused energy, alteration of uterine vascular supply, or surgical procedures. Factors such as the woman's desire for future pregnancy, the importance of uterine preservation, symptom severity, and tumor characteristics direct the choice of therapeutic approach. The ideal treatment will have the following characteristics: easy to perform, minimally invasive, cost effective, preserves fertility, preserves the uterus, efficacious, acceptable tolerability and durability, and low incidence of myoma recurrence.

GnRH agonists and antagonists in assisted reproduction: pregnancy rate

Although gonadotrophin-releasing hormone (GnRH) antagonists offer many advantages when used in ovarian stimulation, their popularity is lower than expected. GnRH protocols are suspected to yield lower pregnancy rates compared with the long agonist protocol. In the current study, subgroup analyses from the German IVF registry (DIR) were performed to evaluate the hypothesis that GnRH antagonists are often used as second-line medication in patients with difficult medical conditions, and thus pregnancy rates may be biased. Consequently, pregnancy rates in the first six stimulation cycles (low rank cycles) were more favourable in the group treated according to the long protocol, while in the patient group requiring more stimulation cycles (high rank cycles; 7, 9 and 10), numerically higher pregnancy rates were achieved with GnRH antagonist protocols. On the other hand, in a patient collective with equal demographic and clinical features (<35 years, tubal infertility), the long and the GnRH antagonist protocols resulted in similar pregnancy rates, supporting the hypothesis that both stimulation protocols lead to equal results.

Treatment of central precocious puberty

The problems of central precocious puberty (CPP) are serious enough to the patient to deserve treatment. There is a general consensus among paediatric endocrinologists that the treatment of true CPP (i.e., in children young enough to have a formal diagnosis) is indicated in many cases. In children with modestly early puberty who are not fulfilling the diagnostic criteria, this is not the case. The treatment of choice is a gonadotropin-releasing hormone (GnRH) analogue. Prolonged analogues are more effective than short-acting ones and, most importantly, independent of patient compliance. Data on agonists have accumulated over two decades and evidence of effects is rich in girls but sparse in boys. GnRH agonists are generally effective and safe drugs; the suppression of puberty is reversible and there is much information on GnRH agonists for the treatment of CPP showing very few adverse effects and the effects on final height are well documented in girls < 6 years of age. There is some (but not highly convincing) evidence for their effect on final height for those of 6 - 8 years of age and there is no evidence for an increase in final height after the age of 8 years in girls. If a decision to have treatment is taken, treatment should start immediately as a possible benefit is less probable if the start of treatment is delayed. When treatment should be stopped is a matter of controversy. Combination with growth hormone increases final height, but the clinical relevance can be discussed as well as the health economy aspects. The limits of indications are still to be defined.

New developments in the use of peptide gonadotropin-releasing hormone antagonists versus agonists

Gonadotropin-releasing hormone (GnRH) stimulates the pituitary secretion of both luteinising hormone (LH) and follicle-stimulating hormone (FSH), and thus controls the hormonal and reproductive functions of the gonads. The blockade of the effects of GnRH may be sought for a variety of reasons; for example, to control premature LH surges and to reduce the cancellation rate with the aim of improving the pregnancy rate per treatment cycle or in the treatment of sex hormone-dependent disorders. Selective blockade of LH/FSH secretion and subsequent chemical castration have previously been achieved by desensitising the pituitary to continuously administered GnRH or by giving long-acting GnRH agonists. GnRH analogues are indicated for clinical situations in which the suppression of endogenous gonadotropins (precocious puberty, contraception and controlled ovarian hyperstimulation) or sexual steroids (endometriosis, prostate hyperplasia, cancer and uterine fibroids) is desired. The immediate suppression of the pituitary that is achieved by GnRH antagonists without an initial stimulatory effect is the main advantage of these compounds over the agonists. GnRH antagonists have been developed for clinical use with acceptable pharmacokinetic, safety and commercial profiles. In assisted reproduction, these compounds seem to be as effective as established therapy, but with shorter treatment times, less use of gonadotropic hormones, improved patient acceptance, and fewer follicles and oocytes. All of the current indications for GnRH agonist desensitisation may prove to be indications for a GnRH antagonist, including endometriosis, leiomyoma and breast cancer in women, benign prostatic hypertrophy and prostatic carcinoma in men, and central precocious puberty in children. However, the best clinical evidence has been in assisted reproduction and prostate cancer.

Extrapituitary effects of GnRH antagonists in assisted reproduction: a review

GnRH antagonists are used to prevent premature LH surges in assisted reproduction. The pregnancy rates obtained in several studies have been similar to those obtained in the long protocol with gonadotrophin-releasing hormone (GnRH) agonists. However, lower oestrogen serum concentrations have been observed and fewer oocytes retrieved using GnRH antagonists. Thus, potential effects at extrapituitary GnRH receptors in the ovary and the endometrium have been claimed. The article reviews the currently available data from the literature as well as current investigations with respect to effects of cetrorelix on the ovary and the endometrium. No evidence was found to support the hypothesis of extrapituitary effects of GnRH antagonists such as cetrorelix at doses used in assisted reproduction.

Patient-friendly ovarian stimulation

The ultimate goal of successful IVF is the birth of a healthy child with no maternal complications. Advances in ovarian stimulation protocols using gonadotrophin-releasing hormone agonists (GnRHa) and high doses of gonadotrophins have resulted in increased oocyte numbers with improved pregnancy and birth rates. However, the efficacy of such therapy is controversial when measured against the potential side effects. These side effects include those arising from oestrogen deprivation during desensitization, complications associated with an increased risk of ovarian hyperstimulation syndrome (OHSS), and an increased possibility of multiple births. Additionally, the increased cost due to more frequent monitoring and increased drug dosage negatively impacts on patient care. Thus, refinements in drug regimens are needed not only to address these side effects, but also to target the quality, not the quantity, of oocytes. In studies comparing GnRH antagonist (GnRHnt) to GnRHa, patients receiving GnRHnt underwent a shorter induction using less gonadotrophin, the incidence of OHSS was reduced and they reported a better quality of life. While larger studies are needed to confirm these promising findings, it appears that milder stimulation protocols could represent an interesting option, at least for selected patients.

No influence of body weight on pregnancy rate in patients treated with cetrorelix according to the single- and multiple-dose protocols

The question of whether adjustment to body weight is necessary in in-vitro fertilization (IVF) cycles using GnRH antagonists is currently under discussion. Therefore, a data analysis of five prospective studies using either the single- or the multiple-dose antagonist protocol with cetrorelix (Cetrotide) was performed. The influence of stimulation procedure, gonadotrophins and body weight on pregnancy rate was evaluated in a linear logit model. The effect of the stimulation procedure and body weight on the cumulus-oocyte complex (COC) and follicle number was explored in an ANOVA model. Cetrorelix plasma concentrations were tested for any correlation with body weight. Baseline and outcome parameters in different body weight groups (<50 kg, 50-59 kg, 60-69 kg, 70-79 kg, > or =80 kg) were assessed for human menopausal gonadotrophin and recombinant human FSH stimulation separately. Cetrorelix plasma concentrations were correlated with body weight, but no influence of the type of stimulation or body weight on pregnancy rate was found. Body weight did not influence cetrorelix plasma concentrations. In contrast, body weight significantly influenced the number of retrieved COC as well as the number of follicles on the day of human chorionic gonadotrophin administration. Body weight does not influence the outcome of treatment in cetrorelix cycles.

Safety and efficacy of a 3 mg dose of the GnRH antagonist cetrorelix in preventing premature LH surges: report of two large multicentre, multinational, phase IIIb clinical experiences

Gonadotrophin-releasing hormone antagonists are effective and safe in preventing premature LH surges, a leading cause of cycle cancellation or failure during assisted conception. Two studies assessed two administration regimens for cetrorelix (as Cetrotide): the multiple-dose (MD, 0.25 mg/day, n = 1066) and single-dose (SD, 3 mg, n = 541) protocols. Patient outcomes were very similar: >90% reached criteria for human chorionic gonadotrophin (HCG) administration and underwent oocyte retrieval; embryo transfer was performed in 83-84%; failure to retrieve oocytes was rare (0.8%); on average, 11 follicles > or =10 mm in diameter were seen on the day of HCG administration. The SD protocol was associated with higher numbers of oocytes retrieved and available for insemination, although the numbers of embryos obtained or transferred were comparable. A total of 251 and 121 pregnancies were reported in the MD and SD groups respectively. Pregnancy rates per embryo transfer were 27 and 28% respectively. Severe ovarian hyperstimulation syndrome (OHSS) occurred in <1% of cycles. Twelve per cent of patients reported local reactions to injections in the MD group, compared with 8% in the SD group; none was serious or led to discontinuation. Seventy-three per cent of patients in the SD group received only one injection. These two studies therefore show that the single-dose cetrorelix protocol offers equal efficacy and safety to the MD regimen, while having the advantage of requiring only one injection in most patients.

Induction of follicular growth and ovulation with urinary and recombinant gonadotrophins

Gonadotrophins have been used since the 1930s. By the 1990s, a pure biological extract of FSH was obtained. The increase in the demand for new assisted reproduction techniques led to the creation of recombinant FSH, 99% pure and highly consistent between batches, with no LH activity, and a high specific activity. In gonadotrophin protocols, follicular growth can be monitored with regular ultrasounds and/or hormonal testing, mainly oestradiol in the follicular phase. In assisted reproduction the adoption of ovulation induction strategies with GnRH analogues, control the endogenous secretion of LH, avoiding cancellations due to an early LH surge, and premature ovulation. Depending on the moment when pituitary suppression starts, there are short, ultra-short and long protocols The use of long protocols not only increases pregnancies and live births, it also allows an easier programming and simplifies IVF treatments. Ovarian stimulation entails some risks such as ovarian hyperstimulation syndrome and multiple pregnancies that can be avoided in many cases with an accurate prediction and an active prevention.

Gonadotrophin-releasing hormone antagonists: will they replace the agonists?

Modern gonadotrophin-releasing hormone (GnRH) antagonists such as cetrorelix and ganirelix reliably prevent premature LH surges in controlled ovarian hyperstimulation for assisted reproductive technologies. Cetrorelix and ganirelix are safe and effective compounds. Because of their distinct pharmacological mode of action, it has been possible to achieve a significant reduction of treatment time. Fertilization and pregnancy rates are comparable to those obtained in agonist protocols for ovarian stimulation. No allergic or hyperergic reactions have been reported, and patient compliance is excellent. The fact that GnRH antagonists allow an immediate suppression of gonadotrophin concentrations while preserving pituitary responsiveness to endogenous GnRH provides enormous flexibility in treatment. GnRH antagonists have helped to overcome some major disadvantages of GnRH agonists, especially of the long protocol, which is currently the standard protocol for ovarian stimulation. The mistaken administration of antagonists during early pregnancy is not possible, since they are only administered during ovarian stimulation when a premature LH surge may be imminent. They are used in the spontaneous cycle or after pretreatment with oral contraceptives. Pregnancy can easily be ruled out by testing for human gonadotrophic hormone before onset of gonadotrophin stimulation on the second or third day of the cycle. Since flare-up effects are absent, there is no risk of cyst formation. Hormonal withdrawal symptoms are eliminated, since no period of pituitary suppression occurs, and therefore exogenous gonadotrophins are not required. Overall, the duration of the stimulation cycle is as short as a normal menstrual cycle. The procedure seems to be safer than the long protocol, since the most serious complication, the occurrence of severe cases of OHSS, is reduced. It is also safe with respect to the course of pregnancies and the health of offspring. Both protocols developed so far, the single dose and multiple dose antagonist protocol, are comparable, utilizing data from the large prospective phase IIIb studies. Although several studies have indicated a slight reduction in pregnancy rate with GnRH antagonists as compared with agonists, this problem may be rectified by developing flexible antagonist regimens designed for individual patients. Introducing flexible GnRH antagonist regimens should be the area of research in the near future.

Depot GnRH agonist versus the single dose GnRH antagonist regimen (cetrorelix, 3 mg) in patients undergoing assisted reproduction treatment

The objective of this study was to compare, in a centre with previous experience of gonadotrophin-releasing hormone (GnRH) antagonist use, single administration of a GnRH antagonist [cetrorelix (Cetrotide) 3 mg] with a single administration of a GnRH agonist [Decapeptyl Retard 3.75 mg] in patients undergoing assisted reproduction treatment (n = 307 and 364 respectively). GnRH agonist was administered on the first day of menses, while cetrorelix was administered when the largest follicle reached 14 mm. Ovarian stimulation was performed with recombinant human FSH (r-hFSH; 150-225 IU/day). Human chorionic gonadotrophin (HCG, 10,000 IU) was administered when at least two follicles reached a mean diameter > or =18 mm. Over 90% of patients in both groups reached the criteria for HCG administration and underwent oocyte retrieval and embryo transfer. Duration of FSH therapy (9.95 versus 11.25 days) and cumulative dose of r-hFSH (1604 versus 1980 IU) were significantly reduced (P < 0.01) in the cetrorelix 3 mg group. The number of oocytes retrieved was lower (8.5 versus 11.2; P < 0.01) with cetrorelix, but the number of embryos replaced was similar (2.2 versus 2.3; NS). The pregnancy rates per oocyte retrieval were the same, 24.5%, in the antagonist and agonist groups. This study indicates that although fewer oocytes are recovered, similar pregnancy rates can be achieved with a GnRH antagonist compared with a GnRH agonist. Additionally, a single dose of 3 mg cetrorelix was administered in 84% of patients, thus being simpler and more convenient for patients. Cetrorelix 3 mg may thus be proposed as a first choice for preventing both a premature LH surge and detrimental rises in LH during ovarian stimulation prior to assisted reproduction treatment.

Clomiphene-induced LH surges and cetrorelix

The following rat pituitary cell culture experiments were carried out to find an explanation for the increased premature LH surges in stimulation protocols using clomiphene citrate (CC) and subsequent gonadotrophin with mid-cycle administration of the GnRH antagonist cetrorelix (Cetrotide(R)) in IVF cycles. Rat pituitary cells were pretreated with CC, then stimulated with GnRH with and without co-administration of different concentrations of GnRH antagonist and compared with non-CC-pretreated controls. While lower concentrations of cetrorelix suppressed LH in CC-non-pretreated cells, but not in CC-pretreated cells, higher concentrations of cetrorelix suppressed LH in both groups. CC pretreatment increased the sensitivity of the pituitary for GnRH and reduced the efficacy of subsequent GnRH antagonist. Thus, the elevated risk of premature LH surges in clinical protocols using CC, gonadotrophin and GnRH antagonist could be overcome by increasing the antagonist dose.

Introduction to methods for collecting human gametes in assisted reproduction

The first objective of IVF is the collection of oocytes and spermatozoa. This article reviews the methods of choice for each sex. Collecting oocytes involves laparoscopic puncture and ultrasonographic puncture via transabdominal/transvesical and periurethral/transvesical, transvaginal methods. Male gametes are collected by masturbation, or by aspirating spermatozoa from the epididymis or from the testicle. Sperm collections can be taken from patients with disorders of ejaculation. A brief review of each approach is presented, with a critical analysis of each method.