Gautam N. Allahbadia1 and Rubina Merchant2
(1)
Department of Assisted Reproduction,, Rotunda – The Center for Human Reproduction, Rotunda-Blue Fertility Clinic and Keyhole Surgery Center, 36 Turner Road, #304-05, 3rd Floor, B-Wing, Bandra (W), Mumbai, Maharashtra, 40050, India
(2)
Department of Assisted Reproduction, The Center for Human Reproduction, 36 Turner Road, #304-05, 3rd Floor, B-Wing, Bandra (W), Mumbai, Maharashtra, 40050, India
Gautam N. Allahbadia
Email: gautam@rotundaivf.com
Abstract
The ability of gonadotropin-releasing hormone (GnRH) agonists (GnRH-a), particularly when used in a long protocol, to fine-tune and conveniently program ovarian stimulation cycles with significant advantages in the prevention of premature luteinization and satisfactory clinical outcomes, has made them a preferred inclusion in stimulation protocols for assisted reproduction. GnRH-a may be administered as short-acting daily low-dose injections or as a single long-acting high-dose injection (depot). A remarkable improvement in clinical pregnancy rates has been reported following downregulation with GnRH-a depot formulation and gonadotropin stimulation compared to gonadotropins alone, particularly in hyperandrogenic patients. The higher duration of gonadotropin stimulation and gonadotropin requirement with the long-acting depot, owing to the suggested profound pituitary suppression, is controversial, and no significant differences in clinical outcomes, the levels of endogenous hormones, or time to pituitary desensitization have been reported in a majority of the studies compared with the short-acting daily preparations. Despite comparable pregnancy outcomes, the use of depot GnRH-a in controlled ovarian hyperstimulation (COH) protocols for assisted reproductive technology (ART) is controversial, with some favoring its use in terms of patient compliance and ease of administration, and results, especially with the reduced dose, while others favoring the short-acting daily GnRH-a in terms of cost-effectiveness, and ovarian response in poor responders. However, the GnRH antagonist single-dose protocol has proved to be superior to the depot GnRH-a for COH with advantages of a significantly reduced duration of gonadotropin stimulation and requirement, higher flexibility in treatment, economy, convenience, and safety despite comparable pregnancy outcomes. Poor responders, in contrast, are reported to benefit from a flare-up GnRH-a protocol with a depot formulation compared to the GnRH antagonist, with higher total pregnancy and implantation rates, possibly due to improved oocyte/embryo competence.
Keywords
Depot GnRH agonistsStimulation protocolsLong-acting depotShort-acting daily low-dose injectionsGnRH antagonistsControlled ovarian hyperstimulationPoor respondersAssisted reproductive techniques
Introduction
The introduction of GnRH agonists (GnRH-a) combined with gonadotropins is considered to be one of the most significant events in the development of in vitro fertilization and embryo transfer (IVF-ET) programs [1], with advantages such as prevention of premature ovulation or premature senescence of the oocyte and increased oocyte yield in poor responders [2], increased oocyte quality [3], more supernumerary embryos for cryopreservation [1], convenient programming of oocyte recovery [1, 2], decreased cycle cancellation rates [2], and improved clinical pregnancy rates [1, 2, 4]. The problems, often associated with premature luteinizing hormone (LH) surges and premature luteinization, and thus, cycle cancellations, have efficiently been overcome by “reversible medical hypophysectomy” with GnRH-a, introduced in 1982 [5]. Hence, GnRH agonists are widely used in controlled ovarian hyperstimulation (COH) for assisted reproductive techniques (ART) [6].
The rationale behind the use of GnRH agonists is to downregulate the pituitary, suppressing the release of endogenous gonadotropins and hence, ovarian activity, to facilitate COH with gonadotropins. Following GnRH-a administration, an immediate flare response of pituitary gonadotropin secretion is followed by downregulation and pituitary desensitization akin to medical hypophysectomy. GnRH antagonists, on the other hand, achieve immediate downregulation by blocking the GnRH receptors. Both GnRH agonists and antagonists are used to block the secretion of endogenous gonadotropins in ovarian stimulation programs for assisted reproduction [7].
According to its initiation and duration, GnRH analog use has been divided into three protocols: the long protocol, the short protocol and the and ultra-short protocol. The long protocol is the most widely used protocol, as it has proved to be the best for suppression of high tonic endogenous LH levels, especially in polycystic ovary syndrome (PCOS) and normogonadotropic patients. The short and ultra-short protocols, have mainly been used in poor responders to ovarian stimulation treatment, older or hypergonadotropic patients with ovarian failure, because of the well-known “flare-up phenomenon” [5]. Attempts to use the GnRH-a to stimulate follicle maturation in a “short protocol” have resulted in variable and sometimes, poor results, leading to the development of the long GnRH-a gonadotropin protocol for ovarian stimulation [2]. The long protocol requires GnRHa administration until suppression of ovarian activity occurs, within approximately 14 days [8]. The superiority of the long protocols over the short and ultra-short protocols has been demonstrated in terms of increased clinical and patient compliance, improved efficacy of pituitary downregulation [1], and clinical pregnancy rates [8] with no evidence of an increased risk of pregnancy wastages or teratogenicity in human pregnancies [1].
GnRH-a can be used either as daily low-dose injections or through a single injection containing higher long-acting doses of the drug (depot) [8]. Traditionally, short-acting analogs have been employed because of concerns over long-acting depot preparations causing profound suppression, a longer period of stimulation, and higher doses of gonadotropins compared with short-acting agonists and luteal phase defects, adversely affecting pregnancy and miscarriage rates [1, 3, 4]. Although nasal administration may be suitable for short-term suppression (up to 28 days), it seems likely that long-acting depot preparations will be useful for more prolonged suppression [9]. However, according to a recent meta-analysis, it is unclear which of these two forms of administration is best, and whether single depot administration may require higher doses of gonadotropins [8].
Apart from their use in ART, GnRH analog depots have also been widely used to treat a variety of diseases including prostate cancer, breast cancer, endometriosis, uterine leiomyomas, and central precocious puberty [10]. GnRH analogs are now a well-established means of treating sex-steroid-dependent, benign and malignant disorders [7]. Monthly depot GnRH agonists are the preferred choice of medical treatment for endometriomas before IVF, with an average duration of treatment of 3 months [11]. In this chapter, we shall focus on the use of depot GnRH agonists for COH in ART.
Clinical Discussion
Endocrine Changes following GnRH-a Administration
Long-term pituitary suppression following high-dose GnRH agonist administration [DTrp6GnRH in microcapsules (Decapeptyl CR)], administered on day 3 of the cycle results in peak Triptorelin levels within 48 h and a gradual decline towards pretreatment values in 8 weeks. Administration of Triptorelin depot in the early follicular phase, results in an initial rapid rise in LH and follicle-stimulating hormone (FSH) levels to peak values after 4 h, followed by desensitization of the pituitary within 24 h and a subsequent decline in FSH levels to nearly normal levels. E2 levels are observed to peak at 12 h, returning to the follicular range thereafter. From the fourth till the seventh week after agonist administration, the LH pulse patterns showed a markedly increased pulse interval, decreased pulse amplitude, and a severely decreased mean LH level during which LH responses to GnRH were severely blunted or absent with the restoration of the pre-injection LH pulse pattern and the LH response to GnRH observed during the eighth and ninth week. Estradiol benzoate challenges showed an E2 rise to preovulatory levels in response to the injections. However, no changes were observed in LH and FSH concentrations. Pituitary responsiveness is completely absent in the second week and continues to exist until the eighth week after injection, when the agonist has disappeared from the circulation. These findings suggest profound alterations in GnRH receptor availability and post-receptor pathways that prevent the pituitary from responding to physiological stimuli [12].
Impact of GnRH-a on the Luteal Phase
The effect of long-acting GnRH-a, in the luteal phase during ART cycles varies from one patient to another. Geber et al. [13] evaluated the effect of long-acting GnRH-a, used for pituitary suppression, in the luteal phase of 367 patients undergoing ovulation induction for IVF/ICSI. Patients were stratified according to the period of action of the agonist in the luteal phase: group 1: ≤6 days; group 2: 7–12 days; and group 3: >12 days. Reporting pregnancy rates of 45.2 %, 38.9 %, and 47.4 % in groups 1, 2, and 3, respectively, they concluded no significant association between the duration of depot GnRH-a action in the luteal phase and pregnancy rates [13].
GnRH Agonist Depot versus Gonadotropins Alone
Schmutzler et al. [14] evaluated the role of GnRH-a in hyperandrogenic patients with elevated LH levels and the consecutive development of polycystic ovaries in women undergoing IVF. A single depot injection of 3.6 mg Goserelin on cycle day 22, followed by individualized human menopausal gonadotropin (hMG) stimulation 14 days later (n = 33) was compared to stimulation with hMG alone on cycle day 3 (n = 29). They reported a significantly higher pregnancy rate per transfer (36.4 % vs. 20 %, respectively) and a strikingly lower abortion rate in the GnRH-a/hMG group compared to the hMG-only group, suggesting the benefit of the combined GnRH-a/hMG stimulation as a first-line therapy for hyperandrogenic IVF patients [14].
Influence of the Type of GnRH Agonist
Orvieto et al. [15] compared the use of two depot GnRH-a, Leuprolide and Triptorelin (3.75 mg depot formulations), administered on days 21–23 of the menstrual cycle in long-suppression GnRH-a protocols in 52 women undergoing COH-IVF. Stimulation with gonadotropins was initiated after pituitary desensitization was achieved. No significant differences were observed in the patient age, estrogen and progesterone levels on day of hCG administration, gonadotropin dosage, number of oocytes retrieved, fertilization rate, percentage of high-quality embryos, and number of embryos transferred. However, significantly higher clinical implantation and pregnancy rates were found in the Leuprolide group compared with the Triptorelin group when used in the mid-luteal phase [15].
Depot versus Daily GnRH Agonist Administration
Two different formulations of GnRH-a are now available: short formulations and depot formulations. Some authors have suggested that depot GnRH-a induce a too high pituitary suppression and reduced GnRH-a doses are enough for pituitary suppression during ovarian stimulation [6]. Partial pituitary desensitization, using GnRH agonists, may be sufficient in women undergoing controlled ovarian hyperstimulation for assisted reproduction; however, the minimal effective agonist dose remains to be determined [16]. Several studies [16–26] have attempted to compare the stimulation and clinical outcomes following pituitary desensitization with daily and depot administration of GnRH agonists and ovarian stimulation with gonadotropins in patients undergoing assisted reproduction with IVF/ICSI over the past two decades, with the aim to determine the adequate GnRH agonist dose and mode of administration for effective pituitary desensitization (Table 10.1).
Table 10.1
Daily versus depot GnRH administration
|
Study |
GnRH-a (daily) |
GnRH-a (depot) |
P |
||||||||
|
n |
GnRH-a |
Dose/mode of administration |
Gn |
Stimulation and clinical outcome |
n |
GnRH-a |
Dose/mode of administration |
Gn |
Stimulation and clinical outcome |
||
|
Safdarian et al. (2007) [20] |
91 |
Buserelin |
0.5 mg s.c. reduced to 0.25 mg at the start of hMG |
hMG |
CPR OPR EPL Gn days: 10.6 |
91 |
Triptorelin |
1.87 mg i.m. |
hMG |
CPR OPR EPL Gn days: 11.2 |
NS NS NS <0.03 |
|
Isikoglu et al. (2007) [21] |
52 |
Leuprolide acetate |
0.5 mg/d |
CPR IR AR Gn units Gn days |
51 |
Leuprolide acetate |
1.88 mg |
CPR IR AR Gn units Gn days |
NS NS NS NS <0.01 |
||
|
Lorusso et al. (2004) [28] |
46 |
Triptorelin acetate |
0.1 mg/d s.c. |
45 |
Triptorelin acetate |
3.75 mg s.c. |
|||||
|
Geber et al. (2002) [22] |
167 |
Leuprolide acetate |
hMG |
Gn units Gn days |
292 |
Goserelin |
hMG |
Gn units Gn days |
S: >40 year NS |
||
|
Dal Prato et al. (2001) [16] |
66 |
Triptorelin |
0.1 mg i.m. reduced to 0.05 mg at the start of FSH |
FSH |
CPR: 34.9 % IR: 18.0 % AR: 9.1 % Gn units: 41.0 ± 26 Gn days: 11 ± 1.3 |
66 |
Triptorelin |
3.75 mg s.c. |
FSH |
CPR: 38 % IR: 20.2 % AR: 8.3 % Gn units: 46.0 ± 25.3 Gn days: 11.8 ± 1.5 |
NS NS NS <0.03 <0.002 |
|
Vlaisavljević et al. (2000) [17] |
260 |
FSH-HP |
CPR: 20.2 % DR: 22.1 % |
454 |
FSH-HP |
CPR: 30.2 % DR: 23.4 % |
NS NS |
||||
|
Hsieh et al. (2000) [23] |
158 |
Leuprolide acetate |
0.5 mg/d s.c. |
CPR Gn days |
289 |
Leuprolide acetate |
1.88 mg s.c. |
CPR Gn days |
NS NS |
||
|
Fábregues et al. (1998) [24] |
30 |
Leuprolide acetate |
CPR IR |
30 |
Leuprolide acetate |
CPR IR |
NS NS |
||||
|
Tsai et al. (1995) [18] |
52 |
Leuprolide acetate |
0.5 mg/d s.c. |
hMG 225 IU/d |
CPR: 21.2 % |
48 |
Leuprolide acetate |
1.88 mg s.c. |
hMG 225 IU/d |
CPR: 25.0 % |
NS |
|
Porcu et al. (1995) [25] |
57 |
Leuprorelin |
0.3 mg twice daily/s.c. |
CPR: 25.9 % IR: 12.3 % MR: 28.5 % |
60 |
Leuprorelin |
3.75 mg |
CPR: 29.4 % IR: 11.9 % MR: 26.6 % |
NS NS NS |
||
|
Porcu et al. (1994) [26] |
94 |
Triptorelin |
0.1 mg/d s.c. |
FSH |
CPR: 25.6 % E2 Gn days |
102 |
Triptorelin |
3.75 mg |
FSH |
CPR: 28.7 % E2 levels Gn days |
NS NS NS |
|
Gonen et al. (1991) [19] |
66 |
Buserelin |
Intranasal |
hMG |
CPR: 27.1 % PL: 26.3 % |
57 |
Decapeptyl depot |
– |
hMG |
CPR: 12.3 % PL: 71.4 % |
<0.05 <0.05 |
CPR clinical pregnancy rate, OPR ongoing pregnancy rate, EPL early pregnancy loss, IR implantation rate, DR delivery rate, AR abortion rate, MR miscarriage rate, E2 estradiol, Gn gonadotropin, FSHfollicle-stimulating hormone, hMG human menopausal gonadotropin, NS non-significant
With the view that traditional doses of depot GnRH agonist may be excessive for ovarian stimulation, Safdarian et al. [20] compared half-dose (1.87 mg) depot Triptorelin i.m. with reduced-dose daily Buserelin s.c. (0.5 mg reduced to 0.25 mg at the start of hMG stimulation) in a long protocol intracytoplasmic sperm injection (ICSI) embryo transfer initiated with oral contraceptives pretreatment for 21 days. The depot was followed by Baily s.c. injections of saline, while daily buserelin was administered after bolus injection of i.m. saline [20]. Some authors [18, 21, 23] compared the efficacy of a single reduced half dose of GnRH-a depot (1.88 mg) with a daily low dose (0.5 mg/day; s.c.) of Leuprolide acetate for pituitary desensitization followed by gonadotropin stimulation in a long protocol but without the OC pretreatment. Others [16] compared a single 3.75 mg depot injection (i.m.) of Triptorelin [(D-Trp-6-luteinizing hormone-releasing hormone (LHRH)] to 100 μg Triptorelin (D-Trp-6-LHRH) form of triptorelin daily, which was then reduced to 50 μg at the start of FSH stimulation [26]. Yet other compared a single 3.75 mg i.m. Leuprorelin depot injection versus Buserelin (0.3 mg sc twice daily) [25] for ovarian stimulation for IVF [25].
Clinical Outcomes
Despite the varied GnRH-a doses, stimulation protocols, gonadotropins used, and times and routes of administration of GnRH, no significant differences have been reported in the estradiol concentrations, follicle number, the quantity of oocytes retrieved and fertilized, the number of embryos transferred [16, 18, 23, 24, 26], clinical pregnancy rates per transfer [8, 16–18, 21, 23–26], implantation rates [16, 21, 24, 25], ongoing pregnancy rates [8, 17, 20, 21], rates of early pregnancy loss [16, 20, 21], miscarriage rates [25, 26], or in the rate of severe OHSS [8] between the depot and daily GnRH agonist groups. No differences have been reported in follicular recruitment and growth during gonadotropin treatment, and the endometrial thickness on the day of hCG between patients randomized to a standard long protocol of s.c. Leuprolide acetate or a monthly injection of Leuprolide acetate depot for 4 months before gonadotropin stimulation [24]. A recent meta-analysis of 12 randomized controlled trials (RCTs) that compared depot and daily administration of GnRH-a in long protocols for IVF treatment cycles in couples with any cause of infertility, using various methods of ovarian stimulation concluded that the chance of achieving a clinical pregnancy, live birth or ongoing pregnancy, and severe ovarian hyperstimulation syndrome (OHSS) using daily GnRH-a injections was 30 %, 24 %, and 3 %, respectively, compared to a corresponding chance between 25 % and 35 %, 18 % and 29 %, and 1 % and 6 %, respectively, using a GnRH-a depot [8].
In contrast, Gonen et al. [19] observed significantly higher (P < 0.05) clinical pregnancy rates per ovum pick-up (OPU) (27.1 % vs. 12.3 %, respectively) and significantly lower rates of pregnancy loss (26.3 % vs. 71.4 %; P < 0.05) in patients who received short-acting GnRH-a (Buserelin) + hMG compared to those who received long-acting GnRH-a D-Trp6 (Decapeptyl Depot) + hMG showing the superiority of short-acting GnRH-a over the long-acting agents in achievement of pregnancy and its outcome, though neither was significantly different from the hMG-only protocol [19]. Significantly lower numbers retrieved oocytes, oocytes fertilized, cleaved embryos, embryos transferred, and estradiol levels have been reported in some studies following depot GnRH-a administration compared to the daily GnRH-a patients despite higher gonadotropin doses [24, 27, 28], suggesting that pituitary over suppression, induced by GnRH-a due to greater bioavailability, hence elevated circulating levels of the GnRH-a peptide, causes an increase in the gonadotropin requirement for ART and a reduction in the number of oocytes retrieved and fertilized [27, 28].
Stimulation Characteristics
While few studies have reported a significantly higher gonadotropin requirement [8, 16, 24, 28] and a significantly longer stimulation period [8, 16, 20, 21], others have, however, observed no significant difference in the gonadotropin requirement [21, 23, 26] or the duration of stimulation [22, 24, 26] between the depot and the daily GnRH agonist groups. On the other hand, though Geber et al. [22] observed a higher requirement for gonadotropin ampules in the depot group, this difference was only evident in patients >40 years that started GnRH-a in the follicular phase. Moreover, while the number of follicles aspirated and the number of oocytes retrieved was similar, the incidence of ovarian cysts in patients with >40 years was higher in patients administered GnRH-a daily [22].
Hormone Levels
Some authors [18, 23, 26] reported no statistical differences in baseline estradiol and FSH concentrations, and concentrations of estradiol, LH, and FSH on the day of human chorionic gonadotropin (hCG) administration between depot and daily GnRH-a administration, while others [2] observed significantly lower serum LH and FSH levels after downregulation with 3.75 mg of the GnRH agonist Triptorelin acetate depot compared to a daily dose of 0.1 mg Triptorelin acetate, necessitating significantly higher gonadotropin doses during subsequent ovarian stimulation to achieve comparable levels of serum estradiol and preovulatory follicles [27]. Profound endogenous LH suppression by depot GnRH agonists indicates a need for minimal LH activity in folliculogenesis and oocyte development [27]. There was no evidence of a premature LH surge in either group [18]. Porcu and Dal Prato reported [26] a high incidence of multiple pregnancy in both the groups [26].
Dada et al. [4] reported a significant difference in the suppression of estradiol from initial concentrations on day 15 of analog administration between patients on the short-acting Buserelin, short-acting Nafarelin and the depot formulation Leuprorelin (54 % vs. 72 % and 65 %, respectively; p < 0.05), all commenced in the early follicular phase. They also reported a significant difference in the number of patients satisfactorily suppressed (80 %, 90 % and 90 %, respectivelyp < 0.05), though there were no differences between the analogs by day 21. Similarly there was no difference in hormonal suppression during the stimulation phase or in the implantation, pregnancy, or miscarriage rates among the three agonists. They concluded that with Nafarelin and Leuprorelin, stimulation with gonadotropins may begin after 2 weeks of suppression and that, long-acting GnRH-a is as effective as short-acting analogs, with no detrimental effects on the luteal phase [4].
Time for Pituitary Desensitization
A series of GnRH tests during the late follicular and mid-luteal phases [26] and estradiol levels < 30 pg/mL have been used as an indication of pituitary desensitization and initiation of gonadotropin administration [28]. Lindner et al. [29] evaluated the efficacy of intranasal administration of the short-acting daily GnRH-a (Buserelin acetate; 1.2 mg/day) during the follicular phase (days 1–3; n = 84),GnRH-a (Buserelin acetate; 1.2 mg/day) + 10 mg Medroxyprogesterone acetate (MDA) for 10 days during the early luteal phase (n = 41), and intramuscular administration of the long-acting depot GnRH-a (Triptorelin acetate) + 10 mg MDA for 10 days during the early luteal phase (n = 42). Pharmacological hypogonadotropism was assessed by the evaluation of serum LH, FSH, estradiol (E2), prolactin, and testosterone levels. Pituitary function was assessed by (1) measurement of fluctuations in endogenous LH levels, (2) response to LHRH (GnRH-a) administration, and (3) response to estradiol benzoate (E2 test). Complete pituitary desensitization was only assumed, if all three tests were negative. The LHRH test and the E2 test were shown to be the most reliable indicators of pituitary function. E2 administration led to further reduction of gonadotropin secretion after pituitary desensitization. They observed a significantly reduced desensitization time in the BA + MDA group compared to the BA only group (20.7 ± 10.5 days vs. 41.1 ± 11.7 days; p < 0.01) and a further, non-significant shortening to 15.1 ± 3.0 days in the TA group. Changes in endocrine parameters demonstrated hypogonadotropic hypoestrogenism after initial pituitary stimulation [29].
However, later studies reported no significant differences in the time taken to achieve downregulation between the daily and depot GnRH-a dose [22, 25, 26], suggesting that both routes of GnRH-a have similar effects on pituitary suppression and ovulation induction in ART [22]. Resumption of pituitary activity occurred 7 days after the discontinuation of the daily form and in about 2 months after discontinuation of the depot form [25].
Interpretations
However, despite comparable clinical outcomes among majority of the studies, interpretations with regard to the choice of GnRH agonist for effective pituitary desensitization differ. Some authors concluded that a reduced GnRH dose is enough for pituitary suppression during ovarian stimulation and offers the possibility of a shorter GnRH-a treatment protocol, requiring lower amounts of gonadotropins that should be considered in view of its economic advantage, though it provides no significant improvement in IVF cycle outcome when compared with the depot formulation [16]. Long-term downregulation does not improve pregnancy rates in a general IVF program over the daily dose GnRH agonist [24], but depot GnRH-a may increase the overall costs of IVF treatment owing to a higher gonadotropin requirement and a longer duration of use [8]. Dal Prato et al. [6] suggested that thouth a reduced daily dose of Triptorelin provides no significant improvement in IVF cycle outcome when compared with depot formulation in normally responding women, it seems to improve ovarian response and overall results in poor responding patients [6].
However, others concluded that a single reduced depot dose (1.88 mg) of Leuprolide is as effective as the classical long multi-dose protocol for pituitary desensitization in COH [21] that may offer a useful alternative for pituitary suppression in ovarian stimulation for IVF [18]. The long-acting GnRH-a is an excellent option, as only a single subcutaneous dose is necessary, decreasing the risk of the patient to forget its use and, most important, it does not interfere with the patient’s quality of life [22]. Considering improved patient compliance and preference, depot forms are advantageous [25].
Dose of Depot GnRH-a
Appropriate dosage of the long-acting depot GnRH agonist has not been determined in long protocol for IVF. Envisaging excessive pituitary suppression by depot GnRH agonist for ovarian stimulation, Dal Prato et al. [30] equally randomized 180 patients to a standard full-dose (3.75 mg) and half-dose (1.87 mg) depot Triptorelin, in a long protocol to compare the efficacy of the two doses. They reported no premature LH surge, higher LH levels (1.04 ± 0.05 vs. 0.7 ± 0.06 IU/L on the day of hCG), lower number of FSH ampules (42 ± 2 vs. 59 ± 3), and significantly higher numbers of mature oocytes (10.1 ± 0.54 vs. 7.4 ± 0.55), fertilized oocytes (8.24 ± 0.35 vs. 6.34 ± 0.37) and of embryos (7.8 ± 0.36 vs. 5.9 ± 0.37) in the half-dose group compared to the full-dose group. No significant differences were found in pregnancy (38.8 % vs. 25.3 %), implantation (22.6 % vs. 13.8 %), or abortion (6.1 vs. 5.0 %) rates. Cumulative pregnancy (fresh plus frozen embryo transfers: 56.8 vs. 35.4 %) rate was significantly higher in the half-dose group. Hence, a half-dose of depot Triptorelin can be successfully used in ovarian stimulation for IVF and produces a higher number of good quality embryos with a good chance of implantation [30]. When these doses were compared in a smaller study (n = 120), Yim et al. [3] also reported significantly lower LH levels at 2 and 3 weeks (2.2 ± 1.0 and 1.1 ± 0.6 IU/L vs. 3.5 ± 5.5 and 2.7 ± 1.9 IU/l, respectively) in the conventional dose (3.75 mg) group compared to the half-dose (1.87 mg) group, respectively, but no significant differences between the doses of gonadotropins used, the number of oocytes and embryos available and the time to resumption of menses, nor in the pregnancy rates. Suppression was measured by evaluating serum LH levels at 2 and 3 weeks after the administration of the GnRH analogs, the dose of gonadotropin used, and the time to resumption of menses. The authors concluded that although the degree of suppression, as measured biochemically, was more profound with the conventional dose, this did not affect the IVF outcome; hence, the use of a lower dose would be equally effective and could contribute to a reduction in the cost of treatment [3].
In a recent study, Li et al. [31] compared further reduced doses: a one-third-dose (1.25 mg) depot Triptorelin with half-dose (1.87 mg) in a luteal long protocol in 100 patients undergoing IVF/ICSI. While no LH surge was observed in both the groups on day 3–5 of the menstrual cycle after downregulation, fewer patients showed low-level LH (<1.0 IU/L) and estradiol (<30 pg/mL) in the one-third-dose group (p < 0.05). They reported fewer retrieved oocytes (p = 0.086), significantly fewer total embryos and available embryos for cryopreservation (p < 0.05), a significantly higher good quality embryo rate (p < 0.05), non-significantly lower length and dose of ovarian stimulation and no significant differences in the clinical pregnancy (52 % vs. 40 %), implantation (48 % vs. 37.5 %), delivery (46 % vs. 32 %), or live birth (42 % vs. 32 %), and the abortion rates (8 % vs. 20 %) rates between the one-third and half-dose groups, respectively. The authors concluded that a one-third-dose depot Triptorelin (1.25 mg) can be successfully used with reduced pituitary suppression and lower cost in a long protocol for IVF [31].
Olivennes et al. [32] compared the ovarian response following a low-dose GnRH agonist protocol and a GnRH agonist long protocol depot formula in patients with high day 3 FSH (>6.5 IU/L). They reported a better ovarian response with the low-dose GnRH agonist with fewer ampules (37.1 vs. 46.6), a shorter duration of stimulation (10.5 vs. 12.4 days), a higher number of mature oocytes (5.9 vs. 4.5), a higher number of good quality embryos (3.2 vs. 2.3), higher E2 levels on day 8 (1065 vs. 460 pg/mL), and lower cancellation rates (14 % vs. 26 %) compared to the depot formula. However, randomized studies are needed to confirm these data [32].
Choice of Gonadotropins
With regard to the choice of gonadotropin stimulation (225 IU/day pure FSH or 225 IU/day hMG) following downregulation with an luteinizing hormone-releasing hormone (LHRH) agonist (Goserelin) depot, Gerli and Villani [33] reported no significant difference in the number of days and ampules required for follicular maturation, number of follicles developed, or in the pregnancy rates between the groups. However, estradiol values at the end of stimulation were significantly lower for the FSH group, suggesting that the contemporary administration of LH with FSH does not exert any effect on follicular development, but it seems to facilitate E2 synthesis, probably by providing more substrate for the aromatization process [33].
Balasch et al. [34] compared ovarian responses after ovarian stimulation with depot GnRH-a protocol combined with recombinant human FSH (rh-FSH) or hMG in normo-ovulatory patients undergoing ICSI. A fixed regimen of 150 IU rh-FSH or hMG was administered in the first 14 days of treatment. Although the dynamics of ovarian follicle development and serum estradiol concentrations on the day of hCG injection during gonadotropin treatment were similar in both the groups, the duration of treatment and the per cycle gonadotropin dose were lower in the hMG group. The number of leading follicles (>17 mm in diameter) on the day of hCG injection was higher and the number of oocytes, mature oocytes, and good quality zygotes and embryos obtained was significantly increased in the rh-FSH group. Hence, though supplemental LH may be required in terms of treatment duration and gonadotropin consumption, both oocyte, embryo yield and quality were significantly higher with the use of rh-FSH in IVF patients undergoing pituitary desensitization with a depot GnRH agonist preparation [34]. However, the choice of gonadotropins that may be used largely depends on the GnRH protocol used and the indication for infertility.
GnRH Agonist Depot versus GnRH Antagonist
Several studies have attempted to compare the outcomes of stimulation with the GnRH agonist long protocol and the GnRH antagonist protocol, followed by gonadotropin stimulation. Olivennes et al. [35] reported a shorter duration of stimulation, lower number of hMG ampules administered, lower occurrence of OHSS, and excellent patient tolerance with a single 3 mg dose of Cetrorelix (administered in the late follicular phase) but a lower number of oocytes and embryos compared to a depot preparation of Triptorelin (Decapeptyl) followed by ovarian stimulation with hMG (Menogon) in patients undergoing IVF-ET. No premature LH surge (LH level >10 IU/L, progesterone level >1 ng/L) was demonstrated after Cetrorelix administration. There was no difference in the percentage of mature oocytes and fertilization rates between the groups, and the pregnancy rates were not statistically different, suggesting that the Cetrorelix single-dose protocol compares favorably with the long protocol and could be a protocol of choice in IVF-ET [35]. Del Gadillo et al. [36] compared a flexible GnRH antagonist (GnRH-ant) protocol (Cetrorelix, 0.25 mg/day, administered when follicles reached a diameter of ≥14 mm) with a GnRH-a Triptorelin long protocol, which was continued during the gonadotropin hMG and/or r-FSH treatment until the induction of ovulation. The authors observed no difference in the mean length of stimulation and the dose of FSH required per patient but a significantly higher mean E2 level on the day of hCG administration (2076 ± 1430 vs. 1145 ± 605 pg/mL), a higher number of oocytes (6.34 vs. 5.38), higher fertilization rate (63.6 % vs. 59.3 %), and a higher pregnancy rate (15 % vs. 5 %) in the GnRH agonist compared to the GnRH antagonist protocol. The authors concluded that GnRH-ant and GnRH-a provide comparable results in unselected patients; however, GnRH-ant allows a higher flexibility in the treatment [36].
Roulier et al. [37] reported a significantly reduced (p < 0.01) duration of FSH therapy (9.95 vs. 11.25 days), cumulative dose of rh-FSH (1604 vs. 1980 IU) and number of oocytes retrieved (8.5 vs. 11.2) following a GnRH-ant flexible protocol [Cetrorelix (Cetrotide) 3 mg, administered when the largest follicle reached 14 mm; n = 307] compared to the administration of a GnRH agonist [Decapeptyl Retard 3.75 mg; n = 364]. On the first day of menses, ovarian stimulation was carried out with rh-FSH, 150–225 IU/day, in both the protocols. Human chorionic gonadotropin, 10,000 IU, was administered when at least two follicles reached a mean diameter ≥18 mm. However, there was no difference in the number of embryos transferred or in the pregnancy rates per oocyte retrieval (24.5 %) between the antagonist and agonist protocols. The authors concluded that although fewer oocytes are recovered, the GnRH antagonist is simpler and more convenient for patients and yields similar pregnancy rates compared to the GnRH agonist protocol, with the added advantage of preventing both a premature LH surge and detrimental rises in LH during ovarian stimulation prior to assisted reproduction treatment [37]. A contemporary study also reported statistically significantly lower (p < 0.01) mean number of ampules of FSH (25.9 vs. 34.5, respectively) and the duration of stimulation (9.6 vs. 12.2 days, respectively) in IVF/ICSI patients administered a flexible single-dose GnRH antagonist (Cetrorelix, 3 mg; n = 224) in the late follicular phase, when the mean follicle diameter exceeded 12 mm compared to a single-dose depot GnRH agonist (Goserelin) long protocol (n = 236) for ovarian stimulation for IVF/ICSI. There was no significant difference in the mean number of oocytes retrieved, fertilization, blastulation and blastocyst transfer rates, or in the clinical pregnancy (34.3 vs. 30.1 %) and delivery rates (31.9 vs. 28.3 %) per cycle between the Goserelin and Cetrorelix groups, respectively. The authors concluded that the flexible single-dose GnRH antagonist protocol is an advantageous alternative to the long GnRH agonist protocol, with similar efficacy, shorter duration, a significant reduction in the number of FSH ampules used, and without the menopause-like effects of the GnRH agonist [38].
A more recent study has also reported similar clinical outcomes with the fixed GnRH-ant and low-dose depot GnRH-a long protocols in infertile women with normal ovarian reserve function undergoing IVF or ICSI cycles, with advantages of economy, convenience, and safety with the GnRH-ant protocol [39]. However, a flare-up GnRH-a protocol with a depot formulation is reported to yield a higher total pregnancy and implantation rate in poor responders than a GnRH antagonist, possibly by improving oocyte/embryo competence [40].
Eldar-Geva et al. [41] compared the outcomes of frozen-thawed embryo transfer, using the long GnRH protocol with Triptorelin depot 3.75 mg (n = 215) or 0.1 mg/day (n = 83), or GnRH-ant protocol with either hCG (n = 69) or GnRH agonist (n = 25) for final oocyte maturation. They reported no differences in the implantation rate, clinical pregnancy rate, ongoing pregnancy rate, and embryo survival rate and concluded that the potential for frozen-thawed embryos to implant and develop following transfer is independent of the GnRH analog and the final oocyte maturation protocol used in the collection cycle [41].
Side Effects
Clinical studies with a number of agonists have demonstrated their efficacy in producing a hypogonadal state safely with rapid recovery following cessation of therapy [9]. Ovarian hyperstimulation following the sole administration of GnRH-a is exceedingly rare [42], with a few cases reported in the literature. Weissman et al. [42] reported massive ovarian multifollicular enlargement concomitant with high serum estradiol concentrations following mid-luteal depot administration of Triptorelin using the long protocol and early follicular administration of Triptorelin as daily subcutaneous injections, which resolved spontaneously following expectant management, and Leuprolide acetate starting at the mid-luteal phase [42]. The authors suggested that ovarian hyperstimulation can occur following the sole administration of GnRH-a irrespective of the preparation used and the administration protocol. This rare entity probably represents an exaggerated form of ovarian cyst formation following GnRH-a administration, the underlying pathophysiology of which remains unresolved [42]. Park et al. [43] reported ovarian multifollicular enlargement with high estradiol level following administration of the GnRH depot preparation, Triptorelin (3.75 mg) without gonadotropins in a patient undergoing IVF for oocyte donation. However, a subsequent cycle in the same patient with a low dose of Triptorelin (0.05 mg) did not induce ovarian hyperstimulation and resulted in clinical pregnancy. Since only few such cases have been published, it is unclear what course to follow in subsequent cycles after ovarian hyperstimulation in the first cycle using only GnRH-a [43].
Conclusion
The GnRH-a depot formulation is a good option for pituitary downregulation in COH cycles for ART with advantages of patient compliance and ease of use and comparable clinical outcomes with the short-acting daily GnRH-a preparation. The feared profound pituitary suppression with the conventional dose (3.75 mg) depot GnRH-a preparation may be overcome with the use of reduced doses (1.87 mg/1.25 mg), which have proven to be equally effective. However, the choice of use of the GnRH-a depot formulation over the daily GnRH-a preparation, or the GnRH antagonist, for COH may be individualized according to cause of infertility and rests solely with the clinician.
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