High doses of gonadotrophin-releasing hormone antagonist in in-vitro fertilization cycles do not adversely affect the outcome of subsequent freeze-thaw cycles

Gonadotropin-Releasing Hormone Antagonists

Gonadotropin-releasing hormone (GnRH) antagonists are now widely used in protocols of patients with controlled ovarian hyperstimulation to treat infertility. By competitively binding to the pituitary GnRH receptor, they lead to a rapid suppression of gonadotropins and consecutively sex hormones. In the past, GnRH agonists have been exclusively used for these patients, with the disadvantage of an initial rise of gonadotropins--the flare-up effect. Several trials comparing the agonistic and antagonistic analogs of GnRH found no significant differences in oocyte quality, fertilization and pregnancy rates. Slightly lower implantation and pregnancy rates, and estradiol levels, in patients treated with GnRH antagonists has raised concern about eventual extrapituitary adverse effects. However, no convincing evidence has yet been found for any detrimental ovarian effects of GnRH antagonists. The lower rate of ovarian hyperstimulation syndrome, a potentially severe disadvantage of infertility treatment, is a positive feature of GnRH antagonists. The key point is that GnRH antagonists have been proven to be as effective and safe as GnRH agonists. This broadens the spectrum of indications for GnRH antagonists to sex hormone-dependent disorders like endometriosis, uterine fibroids, and gynecological cancers such as breast and ovarian cancer.

Gonadotropin-releasing-hormone-receptor antagonists

Pulsatile 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 function of the gonads. Blockade of GnRH effects may be wanted for a variety of reasons-eg, to prevent untimely luteinisation during assisted reproduction 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. Only recently have GnRH-receptor antagonists, that immediately block GnRH's effects, 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 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 so far has been in assisted reproduction and prostate cancer.

Gonadotropin-releasing hormone antagonists implications for oocyte quality and uterine receptivity

Until recently, gonadotropin-releasing hormone (GnRH) agonists were the only choice available to physicians for prevention of premature luteinizing hormone (LH) surges in women undergoing controlled ovarian stimulation. The recent FDA approval of GnRH antagonists for this indication gives clinicians some new options. Results of clinical trials to date suggest that, with GnRH antagonists, much shorter treatment regimens with fewer injections and possibly less gonadotropin can achieve good clinical results. In most of the trials performed to date, however, the GnRH antagonist regimens have been associated with a slightly lower pregnancy and implantation rate than the established GnRH agonist protocols. This remains the biggest hurdle to their more general acceptance. Herein, the possible contributing factors are discussed, and the proposal made that differences in serum estradiol patterns preceding oocyte retrieval are the most likely contributing factor.

Use of third generation gonadotropin-releasing hormone antagonists in in vitro fertilization-embryo transfer: a review

Before gonadotropin-releasing hormone agonists (GnRHa) became available, approximately 20% of stimulated cycles within an in vitro fertilization (IVF) program were cancelled due to premature LH surges. By using the GnRHa to prevent LH surges via gonadotrope GnRH receptor down-regulation and desensitization, this percentage decreased to about 2%, and concomitantly, the IVF and pregnancy rates per cycle initiated were increased. Several treatment schedules currently are in use, including the so-called "long protocol," in which the GnRHa is begun in the luteal phase and down-regulation occurs before the start of the gonadotropin-stimulation treatment phase. This is generally the most effective regimen and is presently the most frequently used protocol. However, it has some disadvantages, such as hypoestrogenic side effects and an increase in the number of ampules of FSH or hMG required for adequate stimulation. There is a new generation of GnRH antagonists now clinically available, that has been able to minimize the potential side effects and provide reliable antagonism at the GnRH receptor. These agents seem better suited than GnRHa for assisted reproductive technology (ART) cycles inasmuch as they can prevent LH surges without requiring complete gonadotropin suppression. We have reviewed the current literature concerning their use in IVF cycles.

Ovulation induction disrupts luteal phase function

Abnormalities in the luteal phase have been detected in virtually all the stimulation protocols used in in vitro fertilization, on both the hormonal and endometrial levels. Supraphysiological follicular or luteal sex steroid serum concentrations, altered estradiol: progesterone (E2/P) ratio, and disturbed luteinizing hormone pituitary secretion leading to corpus luteum insufficiency or a direct drug effect have been postulated as the main etiologic factors. Luteinizing hormone supports corpus luteum function, and low LH levels have been described after human menopausal gonadotropin treatment, after gonadotropin-releasing hormone (GnRH)-agonist treatment, or after GnRH-antagonist treatment. These low luteal LH levels may lead to an insufficient corpus luteum function and consequently to a shortened luteal phase or to the low luteal progesterone concentrations frequently described after ovulation induction. A direct effect of the GnRH agonist or GnRH antagonist on human corpus luteum or on human endometrium and thus on endometrial receptivity cannot be excluded, as GnRH receptors have been described in both compartments. Endometrial histology has revealed a wide range of abnormalities during the various stimulation protocols. In GnRH-agonist cycles, mid-luteal biopsies have revealed increased glandulo-stromal dyssynchrony and delay in endometrial development, strong positivity of endometrial glands for progesterone receptors, decreased alphavbeta3-integrin subunit expression, and earlier appearance of surface epithelium pinopodes. These factors suggest a shift forwards of the implantation window. Progesterone supplementation improves endometrial histology, and its necessity has been well established, at least in cycles using GnRH agonists.

Gonadotropin-releasing hormone antagonist: how good is the new hope?

Gonadotropin-releasing hormone agonists have been widely used to prevent luteinizing hormone surges during controlled ovarian stimulation in assisted reproductive technologies. Treatment with gonadotropin-releasing hormone agonists of uterine myoma, endometriosis and some hormone-dependent cancers, such as breast, ovarian, endometrial and prostate cancer, also seems to have a beneficial effect. Gonadotropin-releasing hormone agonists have the disadvantage of inducing an initial stimulatory effect on gonadotropin secretion, necessitating 2-3 weeks before pituitary desensitization is achieved. Gonadotropin-releasing hormone antagonists, on the contrary, cause an immediate inhibition of gonadotropin secretion by competitive blocking of pituitary gonadotropin-releasing hormone receptors. Some advantages of their clinical use in controlled ovarian stimulation have already been demonstrated. Randomized comparative studies are needed to investigate their benefit over gonadotropin-releasing hormone antagonists for myoma and hormone-related disorders.

Gonadotrophin-releasing hormone antagonists for assisted conception

BACKGROUND

Over the last two decades, a long protocol of Gonadotrophin-releasing hormone agonist (GnRHa) to prevent premature LH surges has been the standard treatment for ovarian stimulation in assisted reproduction. In the long protocols (with GnRHa started either in the mid luteal phase or in the early follicular phase of the preceding cycle) gonadotrophin administration is delayed until pituitary desensitization has been achieved, which usually takes 2-3 weeks. Gonadotrophin-releasing hormone antagonists produce immediate suppression of gonadotrophin secretion, hence, they can be given after starting gonadotrophin administration. This will result in dramatic reduction in the duration of treatment cycle and will avoid estrogen deprivation symptoms associated with GnRH agonist induced down-regulation. Assuming comparable clinical outcome, these benefits would justify a change from the standard long protocol of GnRH agonists to the new GnRH antagonist regimens.

OBJECTIVES

To compare the efficacy of gonadotrophin-releasing hormone (GnRH) antagonists with the standard long protocol of GnRH agonists for controlled ovarian hyperstimulation in assisted conception.

SEARCH STRATEGY

Search strategies included on-line searching of the MEDLINE and EMBASE databases and the Cochrane Menstrual Disorders and Subfertility Group's Specialised Register from 1982 to 2001, and hand searching of bibliographies of relevant publications and reviews, and abstracts of scientific meetings.

SELECTION CRITERIA

Only randomised controlled studies comparing different protocols of GnRH antagonists with GnRH agonists in assisted conception cycles were included in this review.

DATA COLLECTION AND ANALYSIS

Data were extracted into 2 x 2 tables. For the primary outcomes, clinical pregnancy per woman randomised and prevention of premature LH surge, the overall common odds ratio (OR) and the risk difference with 95% confidence interval (CI) were calculated after verifying the presence of homogeneity of treatment effect across all trials. Secondary outcomes considered were the number of oocytes retrieved, clinical pregnancy per oocyte retrieval and per embryo transfer, spontaneous abortion, incidence of severe ovarian hyperstimulation syndrome and the amount of gonadotrophins used. Where relevant data were missing or unclear the authors were consulted.

MAIN RESULTS

Five trials comparing the new fixed protocol of GnRH antagonist to the long protocol of GnRH agonist fulfilled the inclusion criteria and were included. In four studies, the multiple low-dose (0.25 mg) antagonist regimen was applied and in one study, the single high-dose (3 mg) antagonist regimen was investigated. In all trials, reference treatment included a long protocol of GnRHa (buserelin, leuprorelin or triptorelin) starting in the mid-luteal phase of the preceding cycle. In comparison to the long protocol of GnRHa, the overall OR for the prevention of premature LH surges was 1.76 (95% CI 0.75, 4.16), which is not statistically significant. There was a significantly fewer clinical pregnancies in those treated with GnRH antagonists (OR 0.78, 95% CI 0.62, 0.97). The absolute treatment effect (ATE) was calculated to be 5%. The number needed to treat (NNT) was 20. There was a statistically significant reduction in incidence of severe ovarian hyperstimulation syndrome, (RR 0.36, 95% CI 0.16, 0.80) using antagonist regimens as compared to the long GnRHa protocol.

REVIEWER'S CONCLUSIONS

The new fixed GnRH antagonist protocol (i.e. with antagonist start fixed on day 6 of gonadotrophin stimulation) is a short and simple protocol with a significant reduction in incidence of severe OHSS but a lower pregnancy rate compared to the GnRH agonist long protocol. There is a non significant difference between both protocols regarding prevention of premature LH surge. The clinical outcome may be further improved by developing more flexible antagonist regimens taking into account individual patient characteristics. The GnRH antagonist flexible regimen should be the area of research in the near future.

Embryo implantation and GnRH antagonists: GnRH antagonists in ART: lower embryo implantation?

Recently, concerns have been raised regarding possible adverse effects of gonadotrophin-releasing hormone (GnRH) antagonists on extra-pituitary reproductive cells and organs, i.e. ovarian cells, oocyte, embryo, endometrium. These concerns are based on numerous in-vitro studies suggesting decreased biosynthesis of growth factors caused by local action of GnRH antagonists. Clinically, it has been shown that the use of high doses (< or =1 mg daily) of GnRH antagonists is associated with low implantation rates in IVF. Although such direct adverse effect of GnRH antagonists cannot be ruled out at this time, so far clinical experience points to profound LH suppression as the major caveat associated with the use of high doses of GnRH antagonists. Very low LH concentrations are associated with aberrant concentrations of oestradiol during ovarian stimulation, which may in turn adversely effect implantation potential. The clinical data available thus far on the use of GnRH antagonists originate from protocols designed for clinical studies. It is predicted that as more clinical experience is gained, and with protocol modifications to suit individual patient response, GnRH antagonists will be comparable with the agonists in terms of cycle outcome.

Embryo implantation and GnRH antagonists: embryo implantation: the Rubicon for GnRH antagonists

When gonadotrophin-releasing hormone (GnRH) was discovered, the agonist and antagonist of GnRH were developed to control the release of FSH and LH by the gonadotrophs. More than 10 years of research were needed to develop a GnRH antagonist free of histamine release. Recent studies have shown that these GnRH antagonists are effective in preventing a rise in LH during ovarian stimulation in IVF. However, a decrease in ongoing pregnancies seems to suggest that implantation rates per transferred embryo are reduced in GnRH antagonist-stimulated cycles. In my opinion, these data highlight an area less well known to clinicians: the role of the GnRH antagonist at the cellular level in extrapituitary tissues. There are sufficient data in the literature suggesting that GnRH antagonist is an inhibitor of the cell cycle by decreasing the synthesis of growth factors. Given that, for folliculogenesis, blastomere formation and endometrium development, mitosis is everything; the interaction between the GnRH antagonist and the GnRH receptor (present in all these cells and tissues) may compromise the mitotic programme of these cells. This is the Rubicon for the GnRH antagonist: to demonstrate irrevocably that, at the minimal doses necessary to suppress LH release, it does not affect processes such as implantation, embryo development and folliculogenesis.