Increasing the daily dose of recombinant follicle stimulating hormone (Puregon®) does not compensate for the age-related decline in retrievable oocytes after ovarian stimulation

Henk J. Out1,8, Didi D.M. Braat2, Bea M.E. Lintsen2, Timur Gurgan3, Orhan Bukulmez3, Oya Gökmen4, Gürhan Keles4, Pedro Caballero5, José M. González5, Francisco Fábregues6, Juan Balasch6 and Roger Roulier7

1 Organon Laboratories Ltd, Science Park, CB4 0FL Cambridge, UK, 2 University Hospital Nijmegen, Department of Obstetrics and Gynaecology, Geert Grooteplein Zuid 16, 6525 GA Nijmegen, The Netherlands, 3 Hacettepe University, Faculty of Medicine, Department of Obstetrics and Gynaecology, Division of Reproductive Endocrinology & Infertility and 4 Zekai Tahir Burak, Teaching and Research Hospital, Ankara, Turkey, 5 Equipo IVI Madrid, C/Santiago de Compostela, 88–Bajo, 28035 Madrid and 6 Department of Obstetrics and Gynaecology, Hospital Clinic, Institut d'Investigacions Biomèdiques August Pi i Sunyer, C/Casanova 143, 08036, Barcelona, Spain and 7 Institut d'Endocrinologie, Médicine la Reproduction, 6, rue Rocca 13, 147 Marseille Cedex 08, France


    Abstract
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
A prospective, randomized, double-blind, multicentre (n = 6) study was conducted to compare the influence of either a 150 or 250 IU daily fixed-dose regimen of recombinant follicle stimulating hormone (FSH, Puregon®) on the number of oocytes retrieved and the total dose used in down-regulated women between 30 and 39 years of age undergoing ovarian stimulation. In all, 138 women were treated with recombinant FSH, 67 with 150 IU and 71 with 250 IU. The number of oocytes retrieved in the low-dose group was 9.1 compared to 10.6 in the high-dose group (not significant). In the 30–33 years of age class receiving the 250 IU dose, a surplus of 4.2 oocytes (14.8 versus 10.6) was found, whereas in the 37–39 age class nearly one oocyte more was retrieved in the 150 IU group (8.1 versus 7.4). The total dose used to reach the criterion for human chorionic gonadotrophin (HCG) administration was 1727 IU for the women treated with 150 IU daily and 2701 IU for the 250 IU treated women (P < 0.001). No significant relationships were found between serum FSH concentrations as obtained in the early follicular phase and the number of oocytes collected, or the total dose. It is concluded that in women between 30 and 39 years of age, the decline in number of oocytes retrieved with increasing age cannot be overcome by augmenting the daily dose of recombinant FSH from 150 to 250 IU.

Key words: age/IVF/Puregon/recombinant FSH/trial


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Dosing schedules of gonadotrophins in women undergoing ovarian stimulation prior to in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) are based on empirical evidence rather than on randomized controlled trials (Van Hooff, 1995Go). For example, it has never been established in properly designed controlled trials whether the dose of follicle-stimulating hormone (FSH) or human menopausal gonadotrophins (HMG) preparations should be maintained at the same level throughout the whole stimulation period or that an incremental or decremental regimen should be preferred.

Recently, a double-blind controlled clinical trial was published comparing 100 IU and 200 IU of recombinant FSH as a fixed daily dose showing a dose-response relationship with the number of oocytes retrieved available for IVF or ICSI (Out et al., 1999Go). However, the clinical pregnancy rates after the fresh embryo transfer were similar and more side-effects were noted with the high-dose regimen.

It is generally believed that in an attempt to overcome the age-related decline in ovarian response after ovarian stimulation, the dose of gonadotrophins should be adjusted upwards (described, e.g. by Sharif et al., 1998). This leads to high consumption of relatively highly-prized medicines. Next to age, high serum FSH concentrations in the early follicular phase are considered signals of declining ovarian reserve and an important marker of IVF outcome (Scott et al., 1989Go). High basal serum FSH levels are usually considered an indication for augmenting the starting dose of gonadotrophins (see, e.g. Jacob et al., 1998).

For both age and basal FSH concentrations, however, evidence from prospective randomized clinical studies is not available to support this. Therefore, we conducted a double-blind, clinical trial, comparing a fixed daily dose of recombinant FSH (Puregon®) of either 150 IU or 250 IU in women between 30 and 39 years of age.


    Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Study design
This was a prospective, randomized, double-blind, multicentre study comparing a fixed dose of 150 or 250 IU of recombinant FSH (follitropin beta, Puregon®; NV Organon, Oss, The Netherlands). The objective of the study was to assess the impact of these dosing regimens in down-regulated women between 30 and 39 years of age undergoing ovarian stimulation prior to IVF or ICSI on the number of oocytes retrieved and total dose used. The study was performed between February 1997 and July 1998, in six specialized infertility centres in France (n = 1), Spain (n = 2), The Netherlands (n = 1), and Turkey (n = 2). The aim was to include 200 patients with ~100 patients in each treatment group. The study was approved by the Ethics Committees of the individual study centres. Each subject had given written informed consent before participating in the study. The study was conducted in compliance with the Declaration of Helsinki and according to the European Community note on Good Clinical Practice for trials on medicinal products in the European Community (CPMP Working Party on Efficacy of Medicinal Products, 1990Go).

Selection of patients
Inclusion criteria were as follows: aged at least 30 and at most 39 years of age at the time of screening; cause of infertility potentially solvable by IVF or ICSI; normal ovulatory cycles with a mean length of between 24 and 35 days; good physical and mental health; and a body mass index (BMI) between 18 and 29 kg/m2.

Exclusion criteria were: infertility caused by endocrine abnormalities such as hyperprolactinaemia, polycystic ovary syndrome, and absence of ovarian function; one ovary and (or) a history of ovarian surgery; severe endometriosis (grade III); previous ovarian stimulation cycles in which fewer than three oocytes were retrieved; chronic cardiovascular, hepatic, renal, or pulmonary disease; a history of (within 12 months) or current abuse of alcohol or drugs; administration of non-registered investigational drugs within 3 months prior to screening.

When all inclusion criteria and none of the exclusion criteria were met, the subject was considered to be eligible.

Study drugs and study procedures
Pretreatment with a gonadotrophin-releasing hormone (GnRH) agonist for pituitary down-regulation was started either on the first day of the menstrual cycle or in the mid-luteal phase, according to the centre's protocol. All available GnRH agonists were allowed except the i.m. depot preparations. Recombinant FSH (batch nos. CP 096025, 096157, 096026 and 097027) was supplied as lyophilized spheres in ampoules containing 50, 100 IU or 150 IU FSH in-vivo bioactivity. For s.c. injection, two ampoules were reconstituted with 1 ml solvent. HCG (Pregnyl®; NV Organon) in doses of 5000 IU per ampoule was supplied to trigger ovulation. For i.m. injection of HCG, two ampoules were reconstituted with 1 ml solvent.

During the admission visit, demographic and other subject variables were obtained. In addition, general medical and gynaecological histories were obtained, a general medical and gynaecological examination was performed, and an endocrinological, biochemical, and haematological analysis of blood was performed. All general medical, biochemical and haematological measurements were performed according to routine procedures of the individual study centres. Eligible subjects were randomized by receiving a subject number from a randomization list corresponding with patient boxes in which the medication was kept. The 50, 100 and 150 IU ampoules were indistinguishable. The randomization was done in blocks of four and was computer-generated using random numbers. The randomization was stratified for age in order to end up with equal numbers of subjects in each treatment group for the age groups 30–36 and 37–39 years.

When oestradiol serum levels were <200 pmol/l, treatment with recombinant FSH was started and continued until at least three follicles >=17 mm diameter had developed. Dose adaptations were not allowed. The maximum treatment period was 3 weeks. HCG (10000IU) was given to trigger ovulation. After oocyte retrieval and IVF or ICSI, a maximum of three embryos was replaced. Luteal phase support was given according to the preference of the treatment centre.

Serum concentrations of oestradiol, progesterone, FSH and luteinizing hormone (LH) were measured at baseline (moment of down-regulation) and on the day of HCG injection using local assays. Cycle monitoring included frequent vaginal ultrasound investigations and oestradiol measurements.

Basal FSH concentrations (days 1–5) were measured by a central laboratory using a time-resolved immunofluorometric sandwich assay (Delfia®, Wallac OY, Finland).

Study end-points
The primary endpoints were the number of oocytes retrieved and the total dose of recombinant FSH used in relation to age. As an exploratory analysis, the relation of the basal FSH concentrations to these endpoints was also investigated.

Secondary variables included the number of follicles >=17, >=15, >=13 and >=11 mm diameter at the day of HCG administration, levels of FSH, LH, progesterone and oestradiol on the day of HCG administration, treatment length, embryo development rate, the number of transferable embryos, clinical pregnancy rate, implantation rate, miscarriage rate and vital pregnancy rate.

Classification of oocytes as either mature or immature, and embryos as type 1, 2, 3 or 4 was done according to previously published criteria (Staessen et al., 1989Go). Types 1, 2 and 3 were considered transferable embryos. The embryo development rate was defined as the number of transferable embryos divided by the total number of oocytes incubated with semen (in conventional IVF) or injected (in ICSI).

The implantation rate was defined as the number of gestational sacs seen on ultrasound examination divided by the total number of embryos replaced. Vital pregnancies were those pregnancies where a fetal heart beat was observed on ultrasound investigation.

Statistical analysis
For the continuous variables, to investigate the treatment effect related to the age of the subjects, the treatment groups were compared by means of an analysis of covariance (ANCOVA). Starting from the full ANCOVA model with age as covariable and treatment and centre as fixed factors and all interactions, the most appropriate models for the primary parameters were derived. This was an ANCOVA with treatment and centre as fixed factors and age as covariate and no interactions. The derived model assumes, e.g. that there are common slopes for treatment by age (no statistically significant interaction treatment by age; P > 0.10) and that each centre has comparable age differences (no statistically significantly interaction centre by age; P > 0.10). This model was also used for all other parameters. For the analysis of serum hormone concentrations, the log transformation was applied.

For dichotomous variables, the treatment groups were compared by means of logistic regression with age as covariable and treatment and centre as fixed factors. The results were presented for the age classes 30–33, 34–36 and 37–39 years.

The statistical analysis was performed for all subjects who received at least one injection of recombinant FSH.

Sample size considerations
With 100 subjects included in each treatment group and under the assumption of common slopes for treatment by age and assuming an SD of 6.4 oocytes for the number of oocytes retrieved and an SD of 2.5 treatment days, a difference of ~2.5 oocytes and a difference of ~1 treatment day could be detected between the two treatment groups with a power of 80% using a two-sided t-test with a significance level of 5%.


    Results
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Study population
In all, 141 women were randomized in six centres. Forty-seven were aged 30–33 years, 43 were 34–36 years, and 51 were between 37 and 39 years of age. Of these, 138 subjects started treatment with recombinant FSH, 67 with 150 IU and 71 with 250 IU. The numbers of patients treated per centre were 11, 20, 22, 24, 30 and 31.

The 150 IU daily dose treatment was given to 16 women between 30 and 33 years (mean 31.4 years, SD 1.4), to 27 women between 34 and 36 years (mean 34.9 years, SD 0.8) and 24 women between 37 and 39 years (mean 37.7 years, SD 0.9). In the 250 IU group, 30 women were between 30 and 33 years (mean 31.4, SD 1.7), 15 were between 34 and 36 years (mean 35.0, SD 0.9), and 26 were between 37 and 39 years (mean 37.9, SD 0.8).

Both groups had comparable demographic and infertility characteristics (see Table IGo). The main causes of infertility were tubal infertility [n = 24 (36%) versus n = 16 (23%) in the low and high-dose group respectively] and male infertility [n = 27 (40%) versus n = 36 (51%)]. The mean duration of infertility was 7.0 years for the 150 IU group and 7.7 years for the 250 IU group. All women were down-regulated at the start of recombinant FSH treatment. Mean oestradiol concentrations prior to ovarian stimulation were 114 and 102 pmol/l in the 150 and 250 IU groups respectively. The corresponding LH concentrations were 1.7 and 1.9 IU/l.


View this table:
[in this window]
[in a new window]
 
Table I. Demographics and infertility characteristics of the groups of women given different daily doses of recombinant follicle stimulating hormone (FHS)
 
Primary endpoints
Results on the primary endpoints are given in Tables II and IIIGoGo. The mean number of oocytes retrieved was 10.6 in the high-dose group compared to 9.1 in the low-dose group (not significant). Nearly 1000 IU recombinant FSH more were used in the women treated with 250 IU daily compared to the 150 IU group to reach the criterion to administer HCG (2701 versus 1727 IU, P < 0.001).


View this table:
[in this window]
[in a new window]
 
Table II. Statistical analysis of the number of oocytes retrieved and total dose used
 

View this table:
[in this window]
[in a new window]
 
Table III. Number of oocytes retrieved and total dose used per centre
 
The number of oocytes retrieved in the various centres ranged from 6.8 to 13.4 in the 150 IU group, and from 8.3 to 15.7 in the 250 IU. A test for treatmentxcentre interaction was significant (P = 0.01). Total doses of recombinant FSH used ranged from 1435 to 1921 IU in the low-dose treated women and from 2401 to 2866 IU in the high-dose group. A statistically significant centrextreatment effect was observed for this variable (P < 0.01).

The overall number of oocytes retrieved decreased significantly in the different age categories 30–33, 34–36, and 37–39 years, from 13.3 to 9.6 and 7.7 respectively (unadjusted means, P < 0.001). Figure 1Go shows the number of oocytes in the different treatment groups per age class. In the 30–33 years of age class receiving the 250 IU dose, a surplus of 4.2 oocytes (14.8 versus 10.6) was found, whereas in the 37–39 age class nearly one oocyte more was retrieved in the 150 IU group (8.1 versus 7.4).



View larger version (45K):
[in this window]
[in a new window]
 
Figure 1. Mean number of oocytes retrieved and average total dose per patient used in different age categories of women receiving a fixed daily dose of 150 (n = 67) or 250 (n = 71) IU of recombinant FSH. Actual values are shown above each bar.

 
There was also a significant relationship between the age classes and the amount of gonadotrophins consumed (P < 0.01). Figure 1Go shows an increase in the total dose used from 1584 IU to 1661 IU and 1888 IU with increasing age group using a fixed daily dose of 150 IU. In the 250 IU group, the total doses used were 2525, 2700 and 2826 IU for the 30–33, 34–36 and 37–39 years of age categories respectively.

Basal FSH concentrations
Basal FSH (day 1–5) concentrations as determined by a central laboratory were 5.97 IU/l (SD = 2.3) in women aged between 30 and 33 years, 6.01 IU/l (SD = 1.6) in the 34–36 years of age category, and 5.92 IU/l (SD = 6.3) in the women between 37 and 39 years of age. There was one outlier, a 39 year old woman with an FSH value of 45.7 IU/l. Mean concentrations in the 150 IU and 250 IU treatment groups were 5.82 IU/l (SD = 2.5) and 5.23 IU/l (SD = 5.5) respectively (not significant). No relationship was observed in the two treatment groups between the basal FSH level and the number of oocytes retrieved or the total dose used.

Secondary endpoints
Results on the secondary variables are given in Table IVGo. The treatment length was slightly longer in the 150 IU treatment group (11.6 days) as compared to the 250 IU group (10.8 days, not significant). No differences between the treatment groups were observed in the number of follicles >=11, >=13, >=15 and >=17 mm diameter on the day of HCG administration. However, there was a statistically significant relationship between increasing age and the decreasing number of follicles of these sizes (P = 0.022 for follicles >=11 mm, P = 0.014 for follicles >=13 and 15 mm, P < 0.01 for follicles >=17 mm).


View this table:
[in this window]
[in a new window]
 
Table IV. Results on secondary parameters
 
FSH concentrations on the day of HCG administration (or 1–3 days earlier) were 13.0 IU/l in the 250 IU group and 9.3 in the 150 IU group (P < 0.001). Progesterone concentrations in the corresponding period were 3.5 and 2.5 nmol/l in the high- and low-dose groups respectively (P < 0.01). No significant differences were noted in the oestradiol and LH concentrations (see Table IVGo). For all four endocrinological parameters, no significant relationship with age was noted.

In total, 75 women (60%) went through ICSI and 51 (40%) received conventional IVF, i.e. 12 women who started treatment did not reach this stage for various reasons. Per group, 31 (52%) and 29 (48%) received ICSI and IVF respectively in the 150 IU treated women, whereas 44 (33%) had ICSI and 22 (67%) IVF in the 250 IU group.

After conventional IVF, the number of transferable embryos in the 150 IU group was 5.7 compared to 4.9 in the 250 IU group. With ICSI, these numbers were 4.7 and 4.5 respectively. With both fertilization procedures, these differences were not significant.

The embryo development rate, defined as the number of transferable embryos divided by the number of oocytes incubated or injected, was significantly higher in the IVF population, treated with the 150 IU daily dose compared to the 250 IU group (67.5 versus 48.5% respectively, P = 0.015). This was not influenced by the various age classes (P-value not significant). In ICSI, the development rates in the two treatment groups were similar (61.1 and 55.1% in the low- and high-dose groups respectively.

The number of embryos transferred was 2.8 in the 150 IU group and 2.7 in the 250 IU group (not significant). The number of embryos frozen was 1.4 and 1.7 in the low- and high-dose groups respectively (not significant).

Implantation rates appeared to be almost twice as high, although not statistically different, with the 150 IU dose regimen (13.2 versus 7.1%). Vital pregnancy rates per started cycle were 14.9% in the low-dose group versus 12.3% in the high-dose group (not significant). Vital pregnancy rates per started cycle in the 150 IU group for the age groups 30–33, 34–36, and 37–39 years were 13.5, 20.9 and 12.4% respectively. For the 250 IU treated women, corresponding percentages were 16.1, 6.2 and 8.0%.

For the secondary variables, significant treatmentxcentre effects were observed for the treatment duration, number of follicles of all sizes on the day of HCG administration, serum concentrations of FSH, LH and progesterone on the day of HCG administration, number of transferable embryos in patients undergoing ICSI, embryo development rate in patients with conventional IVF and number of embryos transferred.

Cycle cancellations
Of 67 women that started in the low-dose group, 62 had oocyte retrieval (93%) and 57 an embryo transfer (85%). In the high-dose group, 66 (93%) women out of 71 that started recombinant FSH treatment had retrieval and 64 (90%) had an embryo transfer. Two women who had oocyte retrieval did not go through to IVF or ICSI because of other unspecified reasons.

Reasons for cancellation in the low-dose group were insufficient ovarian response (n = 4), risk for hyperstimulation (n = 1), no fertilization (n = 3), or other (n = 2); in the high dose group, these reasons were insufficient ovarian response (n = 4), risk for hyperstimulation (n = 1), no fertilization (n = 1), or combination of reasons (n = 1).

Safety
Three women were hospitalized during the treatment period: two in the 150 IU group (extrauterine pregnancy and miscarriage) and one in the 250 IU group (fever with urinary tract infection).

There were no reports of ovarian hyperstimulation syndrome.


    Discussion
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
It is a good practice in medicine to ensure that the amount of drugs administered to treat a disease is as low as possible. In IVF, many drugs are given, including GnRH agonists for down-regulation, FSH preparations for follicular stimulation, HCG for final maturation of the oocyte and triggering of ovulation, and medication for luteal support. The use of so many medicines is generally experienced as an emotional burden. Recombinant FSH has been shown to be more potent than urinary gonadotrophins and enables the administration of lower starting doses in ovarian stimulation and ovulation induction in clomiphene-resistant anovulatory patients (Out et al., 1995Go, 1999Go; Coelingh Bennink et al., 1998Go; Devroey et al., 1998Go; Hayden et al., 1999Go). In this study, it was investigated whether an increase in recombinant FSH dose can overcome an age-related decline in number of oocytes collected. Evidence was provided that an increase in the daily FSH administration from 150 IU to 250 IU leads to more oocytes available for IVF or ICSI when the woman is between 30 and 33 years of age. However, with a further increase in age, not only was the overall number of retrieved oocytes diminished, but also no difference in number was seen when in total approximately 1000 IU of additional recombinant FSH was given. These data suggest that the linear relationship between an ovulatory dose of recombinant FSH given and the ovarian response (Out et al., 1999Go) disappears with age (>33 years). If the biological mechanisms behind this are also applicable for poor responders in general, these data imply that increasing the dose in a second cycle will not increase the number of oocytes, as noted in two previously reported retrospective studies (Pantos et al., 1990Go; Land et al., 1996Go).

There is evidence that the high serum FSH concentrations in the early follicular phase are a better predictor than age for ovarian response after stimulation with urinary gonadotrophins (Toner et al., 1991Go). Other workers (Sharif et al., 1998Go) performed a descriptive cohort study of 344 women undergoing their first IVF cycle and found that both increasing age and basal FSH concentrations were associated significantly with increased total urinary gonadotrophin dose and reduced number of oocytes collected. The current study did not confirm such an association for basal FSH. There are two potential explanations for this. First, its predictive value might be limited because the average basal FSH concentrations were in the normal range. Second, it could be speculated that this lack of association is due to the use of recombinant FSH that, because of its relatively basic isohormone profile (Matikainen et al., 1993Go), may be more effective in stimulating ovaries than the relatively acidic urinary FSH preparations derived from postmenopausal women with high endogenous FSH secretion. In a previous study comparing recombinant and urinary FSH comprising nearly 1000 women (Out et al., 1995Go), the apparent association between number of oocytes retrieved and basal FSH concentrations found in the urinary FSH-treated women was not seen in the recombinant FSH-treated subjects (unpublished observations). Studies on the endogenous serum FSH isohormone profile in women with elevated FSH concentrations are needed to confirm this hypothesis. However, it seems judicious to be prudent about the predictive value of serum FSH concentrations taken during the early follicular phase when the subsequent stimulation is done with recombinant FSH.

Surprisingly, a significantly higher embryo development rate with conventional IVF was seen using the low-dose regimen: more transferable embryos were obtained from the number of oocytes incubated with semen using 150 IU. No clear explanation is apparent for this phenomenon, although it has been speculated that high doses of gonadotrophins as used in IVF might be deleterious and hamper oocyte quality (Ben Rafael et al., 1987Go). However, it needs to be mentioned that a significant treatmentxcentre for this variable was found in the analysis indicating major differences across the centres.

Although not statistically significant, pregnancy rates were slightly higher with the low-dose regimen. Since the study was not set up primarily to investigate pregnancy rates and its statistical power was too low to detect clinically meaningful differences for that parameter, no firm conclusion can be drawn on this. However, it is clear that raising the gonadotrophin does not automatically lead to an increase in (fresh) pregnancy rates.

No case of ovarian hyperstimulation syndrome was reported in this study, which is surprising. It might be related to the relatively low overall pregnancy rates, the stimulation protocol applied or patient selection.

In conclusion, this study has shown that the frequent clinical practice of increasing the gonadotrophin dose with increasing age does not lead to a higher oocyte yield. This observation is in line with a recent recommendation for milder stimulation regimens in IVF (Edwards et al., 1997Go). Hopefully, the use of lower dosages of recombinant FSH and, in the longer term, the substitution of GnRH agonists by GnRH antagonists (Albano et al., 1996Go; Ganirelix Dose-Finding Study Group, 1998) or, perhaps, the use of minimal gonadotrophin stimulation in combination with a GnRH antagonist (Rongieres-Bertrand et al., 1999Go) will contribute to increased convenience of infertility treatment (including lower costs) and a lessening of the emotional burden experienced by infertile couples.


    Acknowledgments
 
The authors wish to thank ABL, Assen; Monique van Eeden, Pascal Harduin, Ellen Hulskotte, Jacqueline van Kuijk, John Mulders, Jean van de Walle, all from Organon, and Karin Rombouts from Quintiles Benelux, for their contribution to this study.


    Notes
 
8 To whom correspondence should be addressed at:e-mail h.out{at}organon.cge.akzonobel.nl Back


    References
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Albano, C., Smitz, J., Camus, M. et al. (1996) Hormonal profile during the follicular phase in cycles stimulated with a combination of human menopausal gonadotrophin and gonadotrophin-releasing hormone antagonist (Cetrorelix). Hum. Reprod., 11, 2114–2118.[Abstract]

Ben Rafael, Z., Benadiva, C.A., Ausmanas, M. et al. (1987) Dose of human menopausal gonadotropin influences the outcome of an in vitro fertilization program. Fertil. Steril., 48, 964–968.[ISI][Medline]

Coelingh Bennink, H.J.T., Fauser, B.C.J.M., Out, H.J. for the European Puregon Collaborative Anovulation Study Group (1998) Recombinant FSH (Puregon) is more efficient than urinary FSH (Metrodin) in clomiphene-resistant normogonadotropic chronic anovulatory women: a prospective, multicenter, assessor-blind, randomised, clinical trial. Fertil. Steril., 69, 19–25.[ISI][Medline]

CPMP Working Party on Efficacy of Medicinal Products (1990) Good Clinical Practice for trials on medicinal products in the European Community. Pharmacol. Toxicol., 67, 361–372.[Medline]

Devroey, P., Tournaye, H., Van Steirteghem, A. et al. (1998) The use of a 100 IU starting dose of recombinant FSH (Puregon®) in in-vitro fertilization. Hum. Reprod., 13, 565–566.[Free Full Text]

Edwards, R.G., Lobo, RA. and Bouchard, P. (1997) Why delay the obvious need for milder forms of ovarian stimulation? Hum. Reprod., 12, 399–401.[ISI][Medline]

Ganirelix Dose-Finding Group (1998) A double-blind, randomized, dose-finding study to assess the efficacy of the gonadotrophin-releasing hormone antagonist ganirelix (Org 37462) to prevent premature luteinizing hormone surges in women undergoing ovarian stimulation with recombinant follicle stimulating hormone (Puregon®). Hum. Reprod., 13, 3023–3031.[Abstract]

Hayden, C.J., Rutherford, A.J. and Balen, A.H. (1999) Induction of ovulation using a starting dose of 50 units of recombinant follicle stimulating hormone (Puregon). Fertil. Steril., 71, 106–108.[ISI][Medline]

Jacob, S., Drudy, L., Conroy, R. and Harrison, R.F. (1998) Outcome from consecutive in vitro fertilisation/intracytoplasmic sperm injection attempts in the final group treated with urinary gonadotrophins and the first group treated with recombinant follicle stimulating hormone. Hum. Reprod., 13, 1783–1787,[Abstract]

Land, J.A., Yarmolinskaya, M.I., Dumoulin, J.C.M. and Evers, J.L.H. (1996) High-dose human menopausal gonadotropin stimulation in poor responders does not improve in vitro fertilization outcome. Fertil. Steril., 65, 961–965.[ISI][Medline]

Matikainen, T., De Leeuw, R., Mannaerts, B. and Huhtaniemi, I. (1993) Circulating bioactive and immuno-reactive recombinant human follicle stimulating hormone (Org 32489) after administration to gonadotropin-deficient subjects. Fertil. Steril., 61, 62–69.[ISI]

Out, H.J., Mannaerts, B.M.J.L., Driessen, S.G.A.J. and Coelingh Bennink, H.J.T. (1995) A prospective, randomized, assessor-blind, multicentre study comparing recombinant and urinary follicle-stimulating hormone (Puregon vs Metrodin) in in-vitro fertilization. Hum. Reprod., 10, 2534–2540.[Abstract]

Out, H.J., Lindenberg, S., Mikkelsen, A.L. et al. (1999) A prospective, randomised, double-blind clinical trial to study the efficacy and efficiency of a fixed dose of recombinant follicle stimulating hormone (Puregon®) in women undergoing ovarian stimulation. Hum. Reprod., 14, 622–627.[Abstract/Free Full Text]

Pantos, C., Thornton, S.J., Speirs, A.L. and Johnston, I. (1990) Increasing the human menopausal gonadotropin dose – does the response really improve? Fertil. Steril., 53, 436–439.[ISI][Medline]

Rongieres-Bertrand, C., Olivennes, F., Righini, C. et al. (1999) Revival of the natural cycles in in-vitro fertilization with the use of a new gonadotrophin-releasing hormone antagonist (Cetrorelix): a pilot study with minimal stimulation. Hum. Reprod., 14, 683–688.[Abstract/Free Full Text]

Scott, R.T., Toner, J.P., Muasher, S.J. et al. (1989) Follicle-stimulating hormone levels on cycle day 3 are predictive of in vitro fertilization outcome. Fertil. Steril., 51, 651–654.[ISI][Medline]

Sharif, K., Elgendy, M., Lashen, H. and Afnan, M. (1998) Age and basal follicle stimulating hormone as predictors of in vitro fertilisation outcome. Br. J. Obstet. Gynaecol., 105, 107–112.[ISI][Medline]

Staessen, C., Camus, M., Khan, I. et al. (1989) An 18-month survey of infertility treatment by in vitro fertilization, gamete and zygote intrafallopian transfer, and replacement of frozen–thawed embryos. J. In Vitro Fertil. Embryo Transfer, 6, 22–29.[ISI][Medline]

Toner, J.P., Philput, C.B., Jones, G.S. and Muasher, S.J. (1991) Basal follicle stimulating hormone level is a better predictor of in vitro fertilisation performance than age. Fertil. Steril., 55, 784–791.[ISI][Medline]

Van Hooff, M.A.H. (1995) The human menopausal gonadotropin (hMG) dose in in vitro fertilization (IVF): what is the optimal dose? J. Assist. Reprod. Genet., 12, 233–235.[ISI][Medline]

Submitted on May 19, 1999; accepted on September 20, 1999.