Characterizing pituitary response to a gonadotropin-releasing hormone (GnRH) antagonist in monkeys: tonic follicle-stimulating hormone/luteinizing hormone secretion versus acute GnRH challenge tests before, during, and after treatment

Administration effects of single-dose GnRH agonist for luteal support in females undertaking IVF/ICSI cycles: A meta-analysis of randomized controlled trials

The aim of the present meta-analysis was to evaluate the effects of the addition of single-dose gonadotropin-releasing hormone agonist (GnRHa) for luteal support on pregnancy outcomes in females partaking in in vitro fertilization or intracytoplasmic sperm injection cycles. In total, the studies were hand-searched from six electronic databases to compare the pregnancy outcomes between single-dose GnRHa administered as luteal phase support (GnRHa group) and regular luteal support (control group). In the GnRHa group, single-dose GnRH agonist were administered at 5/6 days after IVF/ICSI procedures. In the control group, single-dose GnRH agonist was not added during luteal phase support. Only randomized controlled trials were included. Sensitivity analysis was performed using Revman 5.3 software; the high heterogeneity identified in the present analysis was primarily caused by one study included. Following exclusion of this particular study, the meta-analysis results indicated significantly higher rates of ongoing pregnancy or live birth per transfer (P=0.002), clinical pregnancy per transfer (CPR; P=0.001) and multiple pregnancy per pregnancy (P=0.020) in the GnRHa group compared with those in the control group. Meta-analysis of a subgroup of trials with long-acting GnRH-a ovarian treatment protocols indicated that the rate of ongoing pregnancy or live birth (P=0.080), CPR (P=0.090) and multiple pregnancy per pregnancy (P=0.140) were not significantly different between the two groups. However, the results from trials that had used a multi-dose GnRH antagonist ovarian treatment protocol indicated a significantly higher ongoing pregnancy or live birth rate per transfer (P=0.010), CPR per transfer (P<0.0001) and multiple pregnancy rate per pregnancy (P=0.003) compared with those in the control group. The present results suggested that administration of single-dose GnRH agonist in the luteal phase may be an ideal choice for patients undergoing IVF/ICSI therapy.

Will GNRH antagonists be worth the wait?

Gonadotropin-releasing hormone (GnRH) is also known as luteinizing hormone-releasing hormone (LHRH), formerly luteinizing hormone releasing factor (LRF). Since this hormone regulates the secretion of both FSH and LH, we prefer to call it GnRH. GnRH antagonists, as the name implies, are a class of compounds that actively compete with GnRH for the GnRH receptor, thereby neutralizing the effects of GnRH by competitive receptor occupancy. In order to fully appreciate their potential clinical utility, it is first important to comprehend the critical role of GnRH in the regulation of the pituitary-gonadal axis and secondly to familiarize ourselves with the mechanisms of action of GnRH, GnRH agonists and GnRH antagonists.

The role of LHRH agonists and antagonists

Administration of GnRH analogues (agonists as well as antagonists) produces suppression of the pituitary---gonadal axis, thus inhibiting the secretion of LH, FSH and sexual steroids. For this reason, analogs are indicated in all those clinical situations where suppression of gonadotrophins (precocious puberty, contraception) or of sexual steroids (endometriosis, prostate hyperplasia, cancer, uterine fibroids) is desired. For several years GnRH agonists have been used in combination with gonadotrophins for ovarian stimulation for assisted reproduction in order to control premature LH surges and to reduce cancellation rate with improvement of the pregnancy rate per cycle. This effect is obtained after 2 weeks of agonist administration. The immediate suppression of the pituitary achieved by GnRH antagonists without an initial stimulatory effect is the main advantage of these compounds over the agonists. The prevention of a premature LH surge by GnRH antagonists can be obtained by multiple dose or by a single administration. Both protocols offer the following advantages over the agonists: they require fewer ampoules of gonadotrophins, shorter duration of stimulation, there is a preserved pituitary response to GnRH, less risk of ovarian hyperstimulation syndrome and the luteal phase seems to be more preserved. The main disadvantages of the antagonists are that they are expensive and that pregnancy rate appears to be slightly lower than with the agonists. GnRH antagonists will probably replace agonists in ovarian stimulation treatment for assisted reproduction techniques.

Use of a single bolus of GnRH agonist triptorelin to trigger ovulation after GnRH antagonist ganirelix treatment in women undergoing ovarian stimulation for assisted reproduction, with special reference to the prevention of ovarian hyperstimulation syndrome: preliminary report: short communication

A new treatment option for patients undergoing ovarian stimulation is the gonadotrophin-releasing hormone (GnRH) antagonist protocol, with the possibility to trigger a mid-cycle LH surge using a single bolus of GnRH agonist, reducing the risk of developing ovarian hyperstimulation syndrome (OHSS) in high responders and the chance of cycle cancellation. This report describes the use of 0.2 mg triptorelin (Decapeptyl) to trigger ovulation in eight patients who underwent controlled ovarian hyperstimulation with recombinant FSH (rFSH, Puregon) and concomitant treatment with the GnRH antagonist ganirelix (Orgalutran) for the prevention of premature LH surges. All patients were considered to have an increased risk for developing OHSS (at least 20 follicles > or =11 mm and/or serum oestradiol at least 3000 pg/ml). On the day of triggering the LH surge, the mean number of follicles > or =11 mm was 25.1 +/- 4.5 and the median serum oestradiol concentration was 3675 (range 2980-7670) pg/ml. After GnRH agonist injection, endogenous serum LH and FSH surges were observed with median peak values of 219 and 19 IU/l respectively, measured 4 h after injection. The mean number of oocytes obtained was 23.4 +/- 15.4, of which 83% were mature (metaphase II). None of the patients developed any signs or symptoms of OHSS. So far, four clinical pregnancies have been achieved from the embryos obtained during these cycles, including the first birth following this approach. It is concluded that GnRH agonist effectively triggers an endogenous LH surge for final oocyte maturation after ganirelix treatment in stimulated cycles. Our preliminary results suggest that this regimen may prove effective in triggering ovulation and could be said to prevent OHSS in high responders. The efficacy and safety of such new treatment regimen needs to be established in comparative randomized studies.

Luteal phase and clinical outcome after human menopausal gonadotrophin/gonadotrophin releasing hormone antagonist treatment for ovarian stimulation in in-vitro fertilization/intracytoplasmic sperm injection cycles

The luteal phase hormonal profile and the clinical outcome of 69 patients undergoing in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) after ovarian stimulation with human menopausal gonadotrophin (HMG) and the gonadotrophin-releasing hormone (GnRH) antagonist Cetrorelix were analysed. Twenty-four patients received Cetrorelix 0.5 mg (group I) while in 45 patients Cetrorelix 0.25 mg was administered (group II). Human chorionic gonadotrophin (HCG) was used as luteal support. Nine clinical pregnancies were obtained in group I (37.5%) and 12 in group II (26. 6%). These results were not significantly different. Serum progesterone and oestradiol concentrations did not differ between the two groups either in pregnant or non-pregnant patients. An expected decrease of the same hormones was observed 8 days after the pre-ovulatory HCG injection in non-pregnant women. With regard to serum luteinizing hormone concentrations, a decrease was observed 2 days after the pre-ovulatory HCG injection and was maintained at almost undetectable levels throughout the entire luteal phase in both conception and non-conception cycles of group I and group II. This study demonstrates that different doses of GnRH antagonist do not have any impact on the luteal phase of IVF/ICSI cycles when hormonal support is given.

The use of gonadotrophin-releasing hormone antagonists in polycystic ovarian disease

Polycystic ovarian disease (PCOD) is characterized by anovulation, eventually high luteinizing hormone (LH) levels, with increased LH pulse frequency, and hyperandrogenism. As the aetiology of the disease is still unknown, gonadotrophin-releasing hormone (GnRH) antagonists, competitive inhibitors of GnRH for its receptor, are interesting tools in order to study and treat the role of increased LH levels and pulse frequency in this disease. Their administration provokes a rapid decrease in bioactive and immunoactive LH followed by a slower decrease in follicle-stimulating hormone (FSH). In patients with PCOD, the suppression of gonadotrophin secretion eradicates the symptoms of the disease as long as the treatment lasts. Several authors have suggested that increased plasma LH levels have deleterious effects on the fertility of women with PCOD. Indeed, fewer spontaneous pregnancies with more miscarriages are observed when plasma LH levels are high. Assisted reproduction techniques such as in vitro fertilization (IVF) have provided other clues to the role of the LH secretory pattern in women with PCOD. The number of oocytes retrieved, the fertilization rate and the cleavage rate are lower in PCOD patients undergoing IVF and this is inversely correlated with FSH:LH ratio. These abnormalities are corrected when endogenous secretion of LH is suppressed. On the other hand, implantation and pregnancy rates after IVF are similar to those observed in control women. New GnRH antagonists are devoid of side effects and suppress LH secretion within a few hours without a flare-up effect. This action lasts for 10-100 hours. When GnRH antagonists are associated with i.v. pulsatile GnRH, this combination both suppresses the effect of endogenous GnRH and because of the competition for GnRH receptors restores a normal frequency of LH secretion. We have studied two women with PCOD, administering first 10 mg s.c. every 72 hours for 7 days of the GnRH antagonist Nal-Glu, then adding on top i.v. pulsatile GnRH: 10 micrograms/pulse every 90 minutes for 15 days. We thus succeeded in normalizing LH secretion pattern and observed a significant decline in testosterone levels. We failed to induce appropriate ovarian response and ovulation. In conclusion, the combination of GnRH antagonist and GnRH pulsatile treatment can re-establish normal LH secretory pattern in patients with PCOD. The failure to induce ovulation with this regimen suggests the existence of an inherent ovarian defect in women with PCOD.

Evaluation of the impact of concurrent gonadotropin-releasing hormone (GnRH) antagonist administration on GnRH agonist-induced gonadotrope desensitization

OBJECTIVE

To evaluate the impact of chronic GnRH antagonist therapy on the extent of GnRH agonist-induced gonadotrope desensitization.

DESIGN

Prospective and controlled.

SETTING

Primate Research Center.

PARTICIPANTS

Six reproductive age cycling female baboons (Papio cyanocephalus anubis).

INTERVENTIONS

The animals were divided into two groups. Group A received a total of 19 pulses of 0.83 microgram/kg leuprolide acetate (LA) on a 12-hour dosing schedule. Group B received Nal-Lys (3 mg/kg then 1 mg/kg every other day) for 1 week and then added an identical 19 pulses of LA while continuing Nal-Lys therapy.

MAIN OUTCOME MEASURES

Characterization of the gonadotropin response was done by collecting serum samples at -15, 0, 15, 30, 60, 90, 120, 240, and 480 minutes relative to the injection of the LA.

RESULTS

After equivalent baseline responses, the baboons pretreated with Na-Lys had an increased LH and FSH response to the administration of the LA. After a total of 19 pulses of the LA, the Nal-Lys-treated animals had an increased FSH response in comparison to the untreated controls. This indicates that the extent of gonadotrope desensitization was reduced in the presence of the GnRH antagonist.

CONCLUSIONS

The presence of GnRH antagonist reduces the extent of gonadotrope desensitization in response to the administration of repetitive pulses of GnRH agonist.

In vivo effects of a potent GnRH antagonist ORG 30850: physiologic evidence that down-regulation of GnRH receptors does not occur

OBJECTIVE

Our purpose was to determine the pituitary responsiveness to exogenous GnRH in GnRH antagonist-suppressed ovariectomized monkeys.

METHODS

This was a prospective experimental non-human primate study performed at the research laboratories of The Jones Institute for Reproductive Medicine. Seventeen long-term ovariectomized cynomolgus monkeys were studied.

INTERVENTIONS

The GnRH antagonist ORG 30850 was administered to long-term ovariectomized monkeys assigned to one of six groups: single subcutaneous injections in group A (n = 4), 0.3 mg/kg; group B (n = 4), 1.0 mg/kg; and group C (n = 3), 3.0 mg/kg; and six consecutive daily subcutaneous injections in group D (n = 2), 0.3 mg/kg; group E (n = 2), 1.0 mg/kg; and group F (n = 2), 3.0 mg/kg. Blood samples were collected daily from 10 days before treatment until 22 days after treatment, then weekly for 6 additional weeks. Intravenous GnRH stimulation tests (10 micrograms/kg) were performed on the day after vehicle injection (control) and the day after completion of treatment(s), and then at weekly intervals. The main outcome measures were serum levels of LH, FSH, and ORG 30850.

RESULTS

Administration of ORG 30850 resulted in suppression (P < .05) of LH and FSH in all treatment groups. Long-term suppression (greater than 2 weeks) was evident in all primates receiving a cumulative dose of at least 1 mg/kg. Paradoxically, the responsiveness of the pituitary to exogenous GnRH was accentuated during the time of maximal tonic LH/FSH suppression.

CONCLUSIONS

ORG 30850 is a potent long-acting GnRH antagonist. Furthermore, the present in vivo demonstration of heightened pituitary responsiveness to exogenous GnRH emphasizes the divergent mechanisms of action of GnRH antagonists and GnRH agonists.

Evolving role of Gonadotropin-Releasing Hormone antagonists

GnRH antagonists, unlike GnRH agonists, do not act via "downregulation." Instead, GnRH antagonists monopolize the GnRH receptors to such an extent that endogenous GnRH is unable to bind to sufficient numbers of GnRH receptors to provoke release of LH/FSH. This fundamental difference in the mechanism of action of GnRH antagonists versus GnRH agonists is anticipated to result in clinical benefits for certain applications.

Induction of ovulation for assisted reproduction programmes

The decision to use enhancement of the natural ovarian/menstrual cycle to attempt collection of several oocytes during IVF and GIFT cycles has dramatically increased the pregnancy rates. Furthermore, the recovery of multiple fertilizable oocytes allows for cryopreservation of extra or surplus pre-embryos (or embryos), with the consequent reduction in the risk of multiple pregnancies and the improvement of the cumulative pregnancy rate following IVF and GIFT cycles. Here, we have reviewed the underlying physiological mechanisms in the natural ovarian-menstrual cycle. Subsequently, we have analysed the more frequently utilized ovarian stimulatory regimens with special emphasis on the use of gonadotrophins. Several conclusions may be drawn from the experience to date with these methods of ovarian stimulation. Primarily, lower doses of medication, when used appropriately, may result in a more favourable outcome. Most significant, it seems to be beneficial to tailor the dosages and timing of drug administration to the patient's individual response to medication. Because ovarian stimulation therapy is difficult to manage, a major challenge in reproductive endocrinology has been to develop stimulation protocols that would 'ideally' synchronize the development of a cohort of follicles. The development of GnRH analogues (agonists and antagonists) and the experience (both in women and macaques) gained so far when these drugs are used in combination with gonadotrophins, have helped both in the understanding of the underlying physiology and in the improvement of clinical results.

Intermittent GnRH antagonist plus progestin contraception conserving tonic ovarian estrogen secretion and reducing progestin exposure

The present study was designed to evaluate the effectiveness of a once-weekly regimen of GnRH antagonist followed by a progestin as a potential new contraceptive method. On menstrual cycle days 2, 9, 16, and 23 (onset of menses = Day 1) monkeys were divided into two groups: 1) those injected sc with 0.1 mg/kg Nal-Glu GnRH antagonist in saline and those given only vehicle (control). On cycle days 15 to 26, each treated female was administered 25 micrograms norgestimate/day orally. This was continued for three treatment cycles (84 days). Weekly injections of Nal-Glu GnRH antagonist effectively blocked completion of folliculogenesis, ovulation, and corpus luteum function as judged by serum LH, E2, and P levels. Serum progesterone was undetectable (less than 0.1 ng/ml) during the treatment cycles. Importantly, serum estradiol levels during GnRH antagonist plus norgestimate treatments were maintained at 35 +/- 7 pg/ml. Upon the cessation of norgestimate treatment on day 26 in each cycle, menses uniformly began within 2 or 3 days. Regarding recovery, apparently normal and presumably ovulatory menstrual cycles, as judged by timely estradiol elevations, midcycle LH surges, and luteal phase progesterone patterns, were manifest immediately following termination of the final GnRH antagonist plus norgestimate treatment cycle. Endometrial biopsies removed on day 26 of control cycles, and on day 26 of the third treatment cycle revealed appropriate late secretory phase endometrium having tortuous endometrial glands and superficial stromal edema. Histological sections of ovaries removed at the end of the GnRH antagonist plus norgestimate treatment revealed multiple small and medium-sized developing and atretic follicles, having maintained serial ablation of the potentially maturing follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Probing studies on multiple dose effects of antide (Nal-Lys) GnRH antagonist in ovariectomized monkeys

This study was designed to extend evaluation of the long-acting effects of a "third generation" Antide (Nal-Lys) GnRH antagonist on gonadotropin secretion in ovariectomized (OVX) monkeys, with special attention to recrudescence of pituitary gonadotropin secretion after multiple dose treatments, as well as pituitary secretory responsiveness to GnRH. The duration of FSH/LH inhibition by Antide was dose-dependent, as well as being much longer than for Nal-Glu GnRHant; however, full recrudescence of gonadotropin secretion, albeit gradual, did occur. The acute LH secretory response to serial iv boluses of GnRH, in the face of GnRHant-induced suppression of gonadotropin secretion, was transiently accelerated and biologically active. Thereafter, the state of FSH/LH inhibition was resumed chronically. Thus, treatment with Antide produced profound long-term inhibition of tonic gonadotropin levels, yet hyper-responsiveness to exogenous GnRH administration was maintained throughout.

Future directions: anti-hormones in reproductive medicine

Anti-hormones are important in reproductive medicine because they are useful tools that teach us about the normal physiological actions of hormones. They also provide effective therapies to control or treat a variety of pathogenic processes. We expect that the future repertoire of anti-hormones will include the paracrine and autocrine regulators of specific cell functions, in addition to the endocrine systems described here. The availability of recombinant DNA expression systems for an ever larger portion of the human genome will surely accelerate the development of novel anti-hormones.