Jinan Bekir, M.D. Amma Kyei-Mensah, M.D. Seang-Lin Tan, M.D.

FERTILITY AND STERILITY Copyright ~ 1995 American Society for Reproductive Mediciue Vol. 64, No.4, October 1995 Printed on acid-free paper in U. S. A. Administration of progestogens to hasten pituitary desensitization after the use of gonadotropin-releasing hormone agonist in in vitro fertilization-a prospective randomized study Adel G. Shaker, M.D. Rudiger Pittrof, M.D. Jamal Zaidi, M.D. Jinan Bekir, M.D. Amma Kyei-Mensah, M.D. Seang-Lin Tan, M.D. The London Women's Clinic, London, United Kingdom Objective: To assess the effect of administration of adjuvant 1M progestogen to patients undergoing IVF who were not pituitary desensitized after 14 days of GnRH agonist (GnRH-a) administration. Design: Prospective randomized study. Setting: A tertiary referral center for assisted conception. Patients: Forty-nine patients undergoing 51 IVF treatment cycles. Intervention: Patients in whom the endometrial thickness was >5 mm or who had an ovarian cyst> 15 mm after 14 days of GnRH-a administration were recruited if the serum E2 concentration was >27.24 pg/ml (>100 pmolll). Patients in group 1 (n = 22) received a single 1M injection of 100 mg P whereas patients in group 2 (n = 29) did not. Patients in both groups continued to receive SC GnRH-a 500 j.lg/d and had serum E2levels measured every 3 days until the concentrations were ::;;;100 pmolll. Main Outcome Measures: The number of days of GnRH-a administration from recruitment until serum E2 concentration measured::;;; 100 pmolll, number of cycles with withdrawal bleeding, number of days from recruitment to withdrawal bleeding, total dose of hmg used, number of follicles > 14 mm, number of oocytes, number of embryos, and pregnancy rates per cycle commenced and per ET. Results: There were no significant differences in all the above parameters except in the mean number of days from recruitment to onset of withdrawal bleeding, which were 5.33 ± 0.7 (mean ± SEM) and 8.62 ± 1.26 days in groups 1 and 2, respectively. The pregnancy rate per ET was higher in group 1 (38.88%) when compared with group 2 (19.04%). However, this difference was not statistically significant. Conclusions: Adjuvant administration of a single 1M injection of progestogen hastens the onset of withdrawal bleeding in patients who are not pituitary desensitized after 2 weeks of administration of SC GnRH-a. It does not appear to affect the length of time the serum E2 concentrations take to reach basal levels or to alter the ovarian responsiveness to exogenous gonadotropins. Fertil Steril 1995;64:791-5 Key Words: In vitro fertilization, progestogen, pituitary desensitization, gonadotropin releasing hormone agonist Most IVF programs use some form of ovarian stimulation to induce multiple follicular development. This is because, in general, the more oocytes that are recovered the more embryos will be available for transfer or cryopreservation, with an attendant Received December 13, 1994; revised and accepted May 4, 1995. * Reprint requests: Adel G Shaker, M.D., The London Women's Clinic, 113/115 Harley Street, London WIN 1DG, United Kingdom (FAX: 44-0171-4875850). increase in pregnancy rates (PRs). In the past, hmg with or without clomiphene citrate was the stimulation regimen most commonly used. This has been replaced increasingly in recent years by the use of combined GnRH agonist (GnRH-a) and hmg, which has been reported to be associated with higher pregnancy and live birth rates (1). Although GnRH-a and hmg can be used in various protocols, the one most commonly used is the long protocol, which has been reported by various groups to lead to an increase in Vol. 64, No.4, October 1995 Shaker et al. Progestogens and pituitary desensitization in NF 791

the number of oocytes collected, an improvement in PRs, and a reduction in miscarriage rates (1-4). The long protocol of GnRH-a administration allows greater flexibility in timing of hcg administration (5), thus reducing the amount of monitoring necessary and permitting weekend oocyte collections to be avoided largely (6, 7). This allows simplification of IVF therapy (8). The aim of the long protocol is to achieve pituitary desensitization using GnRH-a before commencing ovarian stimulation with hmg. This, in practice, generally is determined by measuring serum E2 concentrations, which should be at basal levels (:527.24 pg/ml [:5100 pmolll]). Although the majority of patients achieve pituitary desensitization within 10 to 14 days (9), a number of them (estimated to be ~20% ofivf treatment cycles in our program) are not desensitized after 2 weeks. As a result, the treatment cycle is prolonged, much to the inconvenience of the patient. In some cases, the delay in commencement of hmg may be >3 weeks, which adds to the patient's anxiety and stress. In these patients, the endometrium is often thick (>5 mm) and there may be an associated ovarian cyst present. With continued administration of the GnRH-a, these patients generally have a menstrual bleed that is associated with a decline of serum E2 levels and thinning of the endometrium. We postulated that the administration ofprogestogens to these patients may increase the likelihood of withdrawal bleeding or reduce the length of time required for withdrawal bleeding to occur and, in doing so, hasten the decline of serum E2 to basal levels. We, therefore, designed a prospective randomized study to test this hypothesis. MATERIALS AND METHODS Over a period of 8 months (March to October 1994), 49 patients who underwent 51 IVF treatment cycles were recruited into the study, which had been approved by the Institutional Ethical Committee. All patients had a baseline vaginal ultrasound (US) scan on either day 2 or 3 of the cycle to exclude relevant uterine or ovarian pathology. Subcutaneous administration of the GnRH-a, buserelin acetate (Suprefact; Hoechst, Hounslow, United Kingdom) was commenced the same day in a dose of 500 J1g daily. A second US scan was performed 14 days later. If, on the second US scan, an ovarian cyst> 15 mm in diameter was noted or an endometrial thickness >5 mm was seen, the serum E2 levels were checked the same day. If the serum E2 concentration was >27.24 pg/ ml (> 100 pmolll), the patient was recruited into the study and informed consent was taken. The patients were randomized prospectively to one of two groups. Randomization was done by drawing sequentially r labeled sealed envelops, each containing a number obtained from a table of random numbers. Patients : in group 1 continued receiving buserelin acetate in the same dose and were given an 1M injection of 100 mg P (Gestone; Paines & Byrne Limited, Surrey, United Kingdom). Patients in group 2 continued receiving SC buserelin acetate but did not have any progestogen. Other than the injection of P, all patients in the study were treated in exactly the same way. All patients were reviewed 6 days later by having a repeat US scan and measurement of the serum E2 concentration. The endometrial thickness and the mean diameter of any ovarian cyst were recorded at the time of US scan. If the serum E2 concentration remained >27.24 pg/ml (>100 pmol/l), it was measured every 3 days subsequently, until the level was :527.24 pg/ml (:5100 pmol/l). Once the serum E2 concentration was :527.24 pg/ml (:5100 pmol/l), hmg was commenced at the appropriate dosage, depending on the patient's age, her baseline serum FSH level, and her response to stimulation in previous treatment cycles. All patients were regularly monitored by US scans until three follicles with a mean diameter ~ 18 mm were seen when 10,000 IU hcg was administered. Serum E2 levels were measured on the day of hcg administration to assess the potential risk of ovarian hyperstimulation syndrome (OHSS). Patients who had serum E2 concentrations >4903.30 pg/ml (18,000 pmol/l) or serum E2 levels >3541.27 pg/ml (13,000 pmol/l) and ~20 oocytes collected were advised to have their oocytes collected but all their embryos frozen for transfer in a subsequent cycle. In cases of poor ovarian response (less than three follicles ~ 14 mm in diameter), the cycle was canceled or converted to lui provided the patient's fallopian tubes were patent. Oocyte collection and ET were performed as described previously (10, 11). The two groups were compared with regard to the serum E2 levels on the day of recruitment, number of days of buserelin acetate administration from recruitment to serum E2 :5 27.24 pg/ml (:5100 pmol! L) (days to desensitization), time from recruitment to onset of withdrawal bleeding, endometrial thickness, and mean diameter of ovarian cyst on the day of recruitment and 6 days later. Response to ovarian stimulation was assessed in terms of the number of days of hmg administration; the total number of hmg ampules administered; number of follicles, 00- cytes, and embryos; and the PRs. Results were analyzed using the nonparametric Mann-Whitney U test to compare the means and X 2 test to compare the PRs. A value of P < 0.05 was deemed significant. RESULTS There were 22 treatment cycles in group 1 and 29 treatment cycles in group 2. The age of the patients, 792 Shaker et al. Progestogens and pituitary desensitization in NF Fertility and Sterility

Table 1 Demographic Characteristics of Patients in Group 1 (Buserelin Acetate and Gestone) and Group 2 (Buserelin Acetate Only) No. of cycles Mean age (y) Length of infertility (y) No. of previous IVF cycles Cause of infertility (No. of patients) Tubal disease Unexplained Male factor Endometriosis Group 1 22 36.0 :+: 0.86* 5.82 :+: 0.71 1.0 :+: 0.27 6 5 10 1 * Values are means:+: SEM. t Not significantly different in all categories. Group 2 29 35.72 :+: 0.69t 5.52 :+: 0.83 1.07 :+: 0.41 duration of infertility, number of previous treatment cycles, and indications for IVF were comparable in the two groups (Table 1). The mean:::'::: SEM serum E2 concentration on the day of recruitment was 656.51 :::'::: 142.19 pg/ml (2,410.05 :::'::: 521.94 pmol/l) in patients in group 1 compared with 342.09 :::'::: 56.39 pg/ ml (1,255.83 :::'::: 207.01 pmol/l) in patients in group 2. The difference was not statistically significant. There was no significant difference in the mean endometrial thickness on the day of recruitment in group 1 as compared with group 2 (8.9 :::'::: 0.6 versus 8.93 :::'::: 0.38 mm). Both serum E2 concentration and endometrial thickness were assessed in all patients 6 days after recruitment. Patients in group 1 had a reduction in mean serum E2 levels to 134.66 :::'::: 31.66 pg/ml (494.36 :::'::: 116.26 pmol/l) compared with 59.62 :::'::: 11.95 pg/ml (218.86 :::'::: 43.89 pmol/l) for those in group 2. The mean endometrial thickness in group 1 after 6 days was 5.5 :::'::: 0.63 mm (mean reduction of 3.09 :::'::: 0.41 mm) compared with 6.38 :::'::: 0.51 mm in group 2 (mean reduction of 2.39 :::'::: 0.33 mm). The mean diameter of any ovarian cyst seen (21 in group 1 and 23 in group 2) on the day of recruitment was 25.47 :::'::: 2.07 and 23.9 :::'::: 1.78 mm in patients in groups 1 and 2, respectively. Six days later there was little change in the mean diameter of the cysts with the mean diameter being 28.36 :::'::: 2.1 and 25.29 :::'::: 1.26 mm in groups 1 and 2, respectively. There was no significant difference in the mean number of days between recruitment and serum E2 concentrations,,; 27.24 pg/ml (,,;100 pmol/l) in group 1 (12.05 :::'::: 1.11 days) and group 2 11.07 :::'::: 1.14 days) (Table 2). The percentage of patients with withdrawal bleeding was 95.23% of cycles in group 1 and 76% in group 2. The length of time from recruitment to onset of withdrawal bleeding was significantly less in group 1 (5.33 :::'::: 0.7 days) compared with group 2 (8.62 :::'::: 1.26 days) (Table 2). The patients' response to ovarian stimulation, in terms ofthe duration ofhmg 9 6 13 1 Table 2 Comparison of Desensitization in Group 1 (Buserelin Acetate and Gestone) and Group 2 (Buserelin Acetate Only) Group 1 Group 2 Endometrial thickness (mm) Day 0 8.90 :!:: 0.6t 8.93 :!:: 0.38:j: Day 6 5.5 :!:: 0.63 6.38 :!:: 0.51:1: Mean reduction (day 0 to day 6) 3.09 :!:: 0.41 2.39 :!:: 0.33:j: Day ofhcg 9.98 :!:: 0.56 10.45 :!:: 0.35:1: E2 levels (pg/ml) Day 0 656.51 :!:: 142.19 342.09 :!:: 56.39:j: Day 6 134.66 :!:: 31.66 59.62 :!:: l1.95:j: Day 9 68.57 :!:: 27.86 39.54 :!:: 12.1O:j: Day 12 20.01 :!:: 5.28 20.73 :!:: 7.01:j: Day 15 8.37 :!:: 3.54 7.13 :!:: 2.87:j: Day 18 6.51 :!:: 2.8 5.46 :!:: 2.49:j: Day 21 2.0 :!:: 1.39 4.51 :!:: 2.19:j: Day ofhcg 2,201.22 :!:: 421.38 1,741.15 :!:: 228.15+ Days from recruitment to Serum E2,;27.24 pg/ml 12.05 :!:: 1.11 11.07 :!:: 1.14:j: Serum E2,;40.86 pg/ml 10.5 :!:: 0.78 9.62 :!:: 0.95:j: Serum E2 2054.48 pg/ml 9.41 :!:: 0.66 9.10 :!:: 0.86:1: Patients with withdrawal bleed (%) 95.23 76:j: Days from recruitment to onset of withdrawal bleeding 5.33 :!:: 0.7 8.62 :!:: 1.2611 * Day 0 refers to the day of recruitment into the study, day 6 is 6 days later, and so on. t Values are means :!:: SEM. :I: Not significantly different. Conversion factor to SI unit, 3.67. II Significantly different at P = 0.02. treatment; total number of ampules of hmg used; number of follicles and oocytes; and number of embryos generated, transferred, or frozen were similar in both groups (Table 3). The endometrial thickness and serum E2 levels were comparable in the two groups on the day of hcg administration (Table 2). Ovarian cysts (> 10 mm in diameter) were still present in 34 patients (66.66%) at the start ofhmg therapy (18 patients in group 1 and 16 in group 2). 29.41 % of those who had a cyst at the beginning of hmg stimulation became pregnant compared with Table 3 Outcome of Treatment in Group 1 (Buserelin Acetate and Gestone) and Group 2 (Buserelin Acetate Only) Group 1 Group 2* Days ofhmg 11.18 :+: 0.51* 11.48 :+: 0.37 NS Total number of hmg ampules 47.27 :+: 6.92 38.59:+: 3.79 NS Follicles> 14 mm 8.14 :+: 0.89 7.62 :+: 0.84 NS Oocytes retrieved 9.82 :+: 1.09 9.1 :+: 1.09 NS Embryos generated 4.36 :+: 0.59 3.69 :+: 0.55 NS Embryos transferred 2.18 :+: 0.25 1.69 :+: 0.22 NS Embryos frozen 0.77 :+: 0.37 0.93 :+: 0.39 NS No.ofETs 18 21 NS Pregnancy rate per cycle 7/22 (31.81):j: 4/29 (13.79) NS Pregnancy rate per ET 7/18 (38.88) 4/21 (19.04) NS * Group 2 not significantly different from group 1. t Values are means:+: SEM. :j: Values in parentheses are percentages. Vol. 64, No.4, October 1995 Shaker et al. Progestogens and pituitary desensitization in IVF 793

5.88% of those who did not have a cyst. In group 1, two cycles were abandoned due to poor response, one due to failure of embryo cleavage, and all embryos were frozen in one cycle. In group 2, three cycles were converted to lui, one was abandoned for poor response, two for failed fertilization, and two ended in having all embryos frozen because of the increased risk of OHSS. Both patients who had all embryos frozen in group 2 became pregnant subsequently after receiving frozen-thawed embryos in frozen ET cycles. The PRs per cycle commenced and per ET were higher in group 1 (31.81% and 38.88%) compared with group 2 (13.79% and 19.04%). The differences between these rates were not statistically significant. DISCUSSION In vitro fertilization has helped thousands ofinfertile couples conceive. Most patients undergoing treatment are highly motivated and willing to endure the demands associated with treatment both in terms of the emotional as well as time commitment. Indeed many patients return for a second course of IVF treatment after having achieved a previous IVF baby (12). Nevertheless, because many patients would undergo several treatment cycles before achieving live birth (13), it is important to try and simplify treatment as much as possible for the benefit of the patient (8). Over the years, this process of simplification has occurred gradually and systematically. For example, oocyte collection is now performed by transvaginal US guidance under sedation and analgesia rather than laparoscopically under general anesthesia (10). Repeated flushing of the follicles at US-guided oocyte retrieval is no longer considered necessary, as aspiration alone produces a comparable oocyte recovery rate (11) and it has been shown that oocytes collected after repeated flushing have a poorer quality (14). This has allowed transvaginal US retrieval of developed oocytes to be performed in a much shorter time and with less discomfort to the patients. With the development of highly accurate vaginal US scanning for monitoring follicular growth, this has largely superseded the need for daily serum E2 measurements. The introduction of the long protocol of GnRH-a has simplified treatment even further. It has been found that, when this protocol is used, there is at least a 3-day window during which hcg can be administered with good results, and the rates of oocyte recovery, fertilization, and embryo cleavage remain optimal (5). This has led to the notion that the amount of monitoring of ovarian stimulation can be reduced greatly because there is no ideal day ofhcg administration that has to be targeted. In practice, this means that a patient only requires two or three US scans per cycle and no serum E2 measurements for monitoring the time of hcg administration (5). This simplicity of monitoring cannot be achieved necessarily if the short protocol of GnRH -a is used (15). Unfortunately, the long protocol of GnRH-a administration is associated with a significant practical problem, namely the variable length of time needed to achieve pituitary desensitization. Most patients achieve pituitary desensitization within 10 to 14 days of GnRH-a therapy (9) and some do so after as little as 7 days (16, 17). However, a proportion will not have achieved pituitary desensitization even after 2 weeks. Although women who require extended GnRH-a administration do equally well as those who achieve desensitization quickly, in terms of number of oocytes recovered, fertilization, and PRs (18), nevertheless, the prolongation of the treatment with repeated scans and venepunctures adds to the stress of treatment. To complicate matters, it remains uncertain whether it is necessary to achieve basal concentrations of serum E2 before commencing gonadotropin stimulation. The aim of the long protocol is to suppress pituitary responsiveness, and to prevent a premature surge of LH and perturbations of LH secretion. Measurement of serum E2 concentrations as a reflection of pituitary desensitization generally is used because it is too tedious to be performing routine GnRH or E2 benzoate challenge tests. It has been shown that there is a variable length of time needed to achieve pituitary suppression depending on the end point chosen. Haines et al. (19) compared the frequency with which pituitary suppression by GnRH-a was achieved according to hormonal (serum LH <5 mlu/ml [<5 lull], serum E2 < 27.24 pg/ ml [< 100 pmol/ld and US (no follicles > 10 mm) criteria. They found that after 3 weeks of administration of intranasal buserelin acetate in a dose of 300 /-Lg three times daily, pituitary suppression was achieved in 85.6% of cases according to the LH level, 47.9% according to the E21evel, and 81.2% according to US criteria. All three criteria were met in only 11.5% of cases (19). Neither E2 nor LH levels were predictive of the sonographic evidence of pituitary suppression nor did they correlate with IVF outcome (19). Similarly, Bider et al. (17) administered 1.5 mg SC buserelin acetate followed by intranasal 1.2 mg buserelin acetate for 3 weeks. They found that suppression of pituitary activity was achieved after 6 days of bus ere lin acetate but serum E21evels continued to decline for the next 3 weeks to <20 pg/ml (conversion factor to SI unit, 3.67). Finally, Wren et al. (16) have shown that most patients on the long buserelin acetate regimen have serum E2 levels <27.24 pg/ml «100 pmol/l) within 7 days. The 794 Shaker et al. Progestogens and pituitary desensitization in IVF Fertility and Sterility

exceptions were patients with polycystic ovaries or those who developed ovarian cysts as a result of the GnRH-a administration. Most recently, Jenkins et al. (20) have shown that, in patients who develop as ovarian cyst after GnRH-a administration, the serum E2 level can remain elevated, even though pituitary desensitization has been achieved as shown by a negative GnRH challenge test. Various workers have used different serum E2 levels as indicative of pituitary suppression, ranging from <27.24 to 54.48 pg/ml «100 to 200 pmolll) (18). A large number of patients in the present study had a rapid decline of serum E2 concentrations to <54.48 pg/ml «200 pmolll) after the menstrual bleed but the decline then slowed and it took many days for the levels to drop to <27.24 pg/ml «100 pmolll). If a serum E2 concentration of 54.48 pg/ml (200 pmolll) was taken as the cutoff point, then only 13.63% of patients in group 1 would not have been suppressed, 12 days after recruitment, compared with 24.13% in group 2. The presence of ovarian cysts (> 10 mm in diameter) on the day of commencing hmg therapy was not detrimental to the outcome of treatment. This is consistent with our previous observation that aspiration of such cysts did not improve the outcome of treatment (21). In summary, there are varying criteria for assessing whether pituitary suppression has been achieved when the long regimen of buserelin acetate is used. It appears that of the different criteria, it generally takes longest for serum E2 concentrations to reach basal levels. Administration of an injection of progestogen hastens the onset of withdrawal bleeding and it well may be sufficient to commence gonadotropin stimulation once a menstrual bleed has occurred, without actually waiting for the serum E2 levels to be <27.24 pg/ml «100 pmolll). In the present study, the PRs were higher in the group that was given Gestone. A larger study will be needed to determine if the difference is indeed a significant one. REFERENCES 1. Tan S L, Maconochie N, Doyle P, Campbell S, Balen A, Bekir J, et al. Cumulative conception and live birth rates after in vitro fertilization with and without the use oflong, short, and ultrashort regimens of the gonadotropin releasing hormone agonist buserelin. Am J Obstet Gynecol 1994; 171:513-20. 2. Neveu S, Hedon B, Bringer J, Chinchole J M, Arnal F, Hu me au C, et al. Ovarian stimulation by a combination of a gonadotropin-releasing hormone agonist and gonadotropins for in vitro fertilization. Fertil Steril 1987;47:639-43. 3. Tan SoL, Kingsland C, Campbell S, Mills C, Bradfield J, Alexander N, et al. The long protocol of administration of gonadotropin-releasing hormone agonist is superior to the short protocol for ovarian stimulation for in vitro fertilization. Fertil Steril 1992;57:810-4. 4. Balen A, Tan SoL, MacDougal MJ, Jacobs HS. Miscarriage rates following in vitro fertilization are increased in women with polycystic ovaries and reduced after desensitization with buserelin. Hum Reprod 1993;8:959-64. 5. Tan SoL, Balen A, EI Hussein E, Mills C, Campbell S, Yovich J, et al. A prospective randomized study of the optimum timing of human chorionic gonadotropin administration after pituitary desensitization in in vitro fertilization. Fertil Steril 1992;57:1259-64. 6. Dimitry ES, Bates SA, Oskarsson T, Magara R, Winston RML. Programming in vitro fertilization for a 5- or 3-day week. Fertil Steril 1991;55:934-8. 7. Abdalla HI, Baber R, Leonard T, Kirkland A, Mitchell A, Power M, et al. Timed oocyte collection in an assisted conception programme using GnRH-analogue. Hum Reprod 1989; 4:927-30. 8. Tan SoL. Simplifying in-vitro fertilization therapy. Curr Opin Obstet Gynecol 1994;6:111-4. 9. Fleming R, Jamieson ME, Coutts JRT. The use of GnRHanalogs in assisted reproduction. In: Matson PL, Lieberman BA, editors. Clinical IVF forum. Current views in assisted reproduction. Manchester, United Kingdom: Manchester University Press, 1990:1-19. 10. Tan SoL, Bennett S, Parsons J. Surgical techniques of oocyte collection and embryo transfer. Br Med Bull 1990;46:628-42. 11. Tan SoL, Waterstone J, Wren M, Parsons J. A prospective randomized study comparing aspiration only with aspiration and flushing for transvaginal ultrasound directed oocyte recovery. Fertil Steril 1992;58:356-60. 12. Tan SoL, Doyle P, Machonochie N, Edwards RG, Balen A, Bekir J, et al. Pregnancy and birth rates of live infants after in vitro fertilization in women with and without previous in vitro fertilization pregnancies: a study of eight thousand cycles at one center. Am J Obstet Gynecol 1994; 170:34-40. 13. Tan SoL, Royston P, Campbell S, Jacobs HS, Betts J, Mason BA, et al. Cumulative conception and live birth rates after invitro fertilization. Lancet 1992;339:1390-4. 14. EI Hussein E, Balen A, Tan SL. A prospective study comparing the outcome of oocytes retrieved in the aspirate with those retrieved in the flush during transvaginal ultrasound directed oocyte recovery for in-vitro fertilization. Br J Obstet Gynaecol 1992;99:841-4. 15. Clark L, Stanger J, Brinsmead M. Prolonged follicular stimulation decreases pregnancy rates after in vitro fertilization. Fertil Steril 1991;55:1192-4. 16. Wren M, Tan SL, Waterstone J, Parsons J. The optimum dose and mode of administration of luteinizing hormone releasing hormone analogue in in-vitro fertilization: a comparison of three regimens. Hum Reprod 1991;6:1370-2. 17. Bider D, Ben-Rafael Z, Shalev J, Goldenberg M, Mashiach S, Blankstein J. Pituitary and ovarian suppression rate after high dosage of gonadotropin-releasing hormone agonist. Fertil Steril 1989;51:578-81. 18. Ibrahim ZHZ, Matson PL, Critchlow JD, Newman MC, Horne G, Hughes S, et al. Use of buserelin in an IVF programme for pituitary-ovarian suppression prior to ovarian stimulation with exogenous gonadotrophins. Hum Reprod 1990;5:258-62. 19. Haines C, Loong E, Chan M, Chung T. A comparison ofhormonal and ultrasound assessment of pituitary suppression after pretreatment with a gonadotropin releasing hormone. agonist. lnt J Fertil 1993;38:355-9. 20. Jenkins JM, Anthony FW, Lee A, Masson GM, Thomas E. Persistent elevation of serum estradiol levels by functional ovarian cysts despite effective pituitary desensitization with GnRH agonists. Clin Endocrinol (OxD 1994;40:357-9. 21. Rizk B, Tan SL, Kingsland C, Steer C, Mason BA, Campbell S. Ovarian cyst aspiration and the outcome of in vitro fertilization. Fertil Steril 1990;54:661-4. Vol. 64, No.4, October 1995 Shaker et al. Progestogens and pituitary desensitization in IVF 795