1 IVF Unit, Department of Obstetrics and Gynecology, 2 Institute of Hormone Research Shaare-Zedek Medical Center, Ben-Gurion University, P.O.Box 3235, Jerusalem 91031, Israel, 3 Prince Henry's Institute of Medical Research and 4 Department of Obstetrics and Gynaecology, Monash Medical Centre, Melbourne, Victoria, Australia
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Abstract |
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Key words: inhibin A/inhibin B/IVF/low responders/oocyte number
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Introduction |
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The ageing of the ovary is accompanied by depletion of primordial and antral follicles (Faddy and Gosden, 1996) and a decrease in inhibin B secretion (Klein et al., 1996
; Danforth et al., 1998
). Early follicular phase serum inhibin B may be a suitable marker of ovarian follicle reserve and fertility potential (Klein et al., 1996
; Seifer et al., 1997
, 1999
; Danforth et al., 1998
). However, several studies found no or limited clinical value in measuring basal early follicular inhibin B with regard to IVF outcome (Corson et al., 1999
; Hall et al., 1999
; Tinkanen et al., 1999
; Creus et al., 2000
; Ravhon et al., 2000
; Dumesic et al., 2001
).
It was found that inhibin B level on day 5 of FSH treatment for IVF was highly predictive of ovarian response (Penarrubia et al., 2000). Another study (Dokras et al., 2000
) observed that inhibin B levels on treatment days 8 to 11 was lower in patients with endometriosis and correlated with the number of oocytes retrieved. Recently, the increment in serum inhibin B 24 h after FSH stimulation in the early follicular phase of the preceding cycle was found to be correlated with the number of follicles in normal cycling women and in women with polycystic ovarian syndrome (PCOS) (Elting et al., 2001
).
In a previous study, we found that following a daily fixed dose administration of FSH, in normal ovulatory young women, serum inhibin B after 46 days of FSH treatment significantly correlated with the number of oocytes retrieved (r = 0.89, P < 0.001) (Eldar-Geva et al., 2000). Other markers used for monitoring ovarian response [estradiol (E2) and follicular number and size] could not predict treatment outcome at this early stage of treatment. The aims of the current study were to examine the significance of earlier inhibin B measurements in predicting the number of oocytes to be retrieved and to assess whether a similar relationship between inhibin B and oocyte number applies to patients with low ovarian response.
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Materials and methods |
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Study A
Nineteen patients either undergoing their first IVF cycle (10 patients) or who had normal response (6 oocytes retrieved, nine patients) in their previous cycles were included in this study. The patients were treated with the long down-regulation protocol consisting of decapeptyl [0.1 mg/day; Ferring Ltd (A.Lapidot Ltd), Herzliya, Israel] s.c. for 14 days, starting in the mid-luteal phase of the ovarian cycle. When E2 concentrations were <150 pmol/l and the presence of any ovarian cysts was excluded by vaginal ultrasound, a fixed daily dose of 300 IU of pure FSH (Metrodin, 75 IU/ampoule; Teva, Petah Tikva, Israel) was administered i.m. Serum samples were collected prior to, and every 12 days throughout, FSH treatment. For the convenience of both the patients and the clinicians, FSH injections were self-administered every day at 20:00 and blood samples were taken at 08:00. The ovarian response was monitored by serum E2 and transvaginal ultrasonography. Serum samples were stored at 20°C until assayed for progesterone, FSH, LH, inhibin A and inhibin B. Treatment was continued for a maximum of 3 weeks until two or more follicles >17 mm developed. hCG (10 000 IU, Chorigon; Teva) was given to promote ovulation. Oocytes were retrieved transvaginally 36 h later under general anaesthesia. Routine IVF or ICSI and embryo culture were used as indicated and a maximum of three embryos were transferred 23 days following oocyte retrieval.
Study B
Fifteen patients with previous low ovarian response (5 oocytes retrieved) to the ordinary FSH treatment dose (300 IU/day) were included in this study. They were also treated with the above long down-regulation protocol; however, a higher daily FSH dose (600 IU) was used. Clinical data of both groups are presented in Table I
.
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Statistical analysis
Samples with hormone values below the assay detection limit were assigned values equal to the detection limit of that assay. Statistical analysis was performed using MannWhitney U-test and Pearson's correlation coefficient as appropriate. Results are expressed as means ± SEM unless otherwise indicated. Differences were considered to be statistically significant if P < 0.05.
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Results |
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The correlation between the number of oocytes retrieved and serum inhibin B and inhibin A were significant on all days of FSH treatment (Table III). Highly significant correlations were noted with inhibin B early during treatment (r = 0.850.90 on days 2, 3 and 4). Significant, but lower, correlations were found with inhibin A on days 2 and 3 of FSH treatment (r = 0.650.68; P < 0.05). Highly significant correlations were found with inhibin A late during FSH treatment (r = 0.860.94; P < 0.001 from days 56 until the last day). No significant correlations were observed between oocyte number and serum E2 levels on any day of treatment.
The regression line for day 2 was linear for a large range of oocyte numbers (013) (Figure 2). Similar to the results of study A, all patients with serum inhibin B >100 pg/ml had >6 oocytes.
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Discussion |
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Provocative tests such as the clomiphene citrate challenge test (CCCT) (Navot et al., 1987) have been shown to be more sensitive than screening with basal day 3 FSH alone, in both the general infertility population and in assisted reproduction patients (Loumaye et al., 1990
; Tanbo et al., 1992
; Scott et al., 1993
). Determining E2 response in the GnRH agonist stimulation test (Garcia et al., 1990
; Padilla et al., 1990
; Galtier-Dereure et al., 1996
; Ranieri et al., 1998
) or the exogenous FSH ovarian reserve test (EFORT) (Fanchin et al., 1994
) seem to improve the predictive value of the basal hormone levels. Previous studies (Ravhon et al., 2000
) have shown that inhibin B and E2 dynamic changes after GnRH analogue administration on cycle day 2 correlated with ovarian response for IVF and were superior to basal hormones levels. Other investigators (Dzik et al., 2000
) have reported that low inhibin B response to EFORT could predict low ovarian response in a subsequent IVF cycle and that E2 response was less informative. Elting et al. showed that the rise of E2 and inhibin B after FSH stimulation in the follicular phase predicts the number of follicles in patients with polycystic ovaries and in young, normal menstruating women (Elting et al., 2001
). Fabregues et al. found that after 5 days of hMG stimulation, serum E2, but not inhibin B level, was a better predictor of ovarian response than basal FSH, inhibin B and E2 levels (Fabregues et al., 2000
). These studies support the assumption that dynamic changes in ovarian hormones could be more sensitive than basal hormone measurement in predicting assisted reproduction outcome. However, dynamic tests performed before the treatment cycle have some disadvantages. A high percentage of cycle-to-cycle variability may change the prognostic value of the CCCT in up to 40% of patients (Hannoun et al., 1998
).
In a previous study, we found that in normal ovulatory young women treated with pituitary suppression and a daily fixed dose of FSH, serum inhibin B after 46 days of FSH treatment significantly correlated with the number of oocytes retrieved (Eldar-Geva et al., 2000). Other investigators found similar correlations after 5 (Penarrubia et al., 2000
) or 810 days (Dokras et al., 2000
) of FSH treatment. The current study shows that in patients with either low or normal ovarian reserve, serum inhibin B levels measured as early as 36 h after commencing FSH treatment (day 2) may indicate whether sufficient oocytes will be collected 1016 days later. In the group of patients with previous low ovarian response, day 2 inhibin B levels could predict the number of oocytes to be retrieved.
The crucial parameter determining the number of oocytes retrieved is the extent of the cohort of recruited healthy very small follicles. The size of this cohort may change from cycle to cycle (Scheffer et al., 1999), especially in elderly patients. We assume that the hormone level intercycle variability represents different cohort sizes at different cycles. The high correlation observed in our study between serum inhibin B levels very early during FSH treatment and subsequent number of oocytes collected in patients with previous low ovarian response, suggests that the measurement of inhibin B may be useful as a marker of ovarian response during early FSH treatment on a specific treatment cycle and under a specific FSH dose in this group of patients.
Our findings might have a clinical implication, although larger studies are needed. For example, in both studies, all patients with day 2 serum inhibin B >100 pg/ml had >6 oocytes retrieved (Figures 1 and 2). Only one patient (Figure 2
) with serum inhibin B <100 pg/ml had >6 oocytes retrieved. This information might be used for reassuringly advising patients with day 2 inhibin B >100 pg/ml to continue the treatment cycle with the same initial daily FSH dose. Patients with day 2 inhibin B <100 pg/ml might be advised either to change the FSH or the GnRH analogue dose, or perhaps to cancel the treatment cycle. Our ability to change treatment outcome late during the course of treatment is limited. Very early during treatment, increasing FSH levels may facilitate the recruitment of more follicles. It is still to be clarified whether modulating FSH or GnRH analogue doses early during FSH treatment would improve outcome. Nevertheless, even if the doctor and/or the patients prefer to cancel the cycle, the earlier this is done the better.
Our results showed that predicting the oocyte number was less effective in high responders, i.e. patients who had >15 oocytes had very wide range of day 2 serum inhibin B (Figure 1). None of these patients had PCOS or OHSS. We assume that repeated FSH doses may continuously recruit ovarian follicles in these patients, while in the low or normal responders (<15 oocytes retrieved) the continuous recruitment is limited. Indeed, serum inhibin B concentrations reached the maximum later in study A than in study B (Figure 3
).
In study A, inhibin A, and to a lesser extent E2 levels, correlated with the number of oocytes retrieved. In contrast, in study B, although highly significant correlations were found with inhibin A late during treatment, no correlation was found with E2 levels on any day of the treatment (Table III). Dokras et al. observed similar results in patients with endometriosis and low ovarian response, compared with patients with tubal factor infertility and normal response (Dokras et al., 2000
). A decrease in inhibin B is the earliest marker of the decline in follicle number across reproductive ageing (Seifer et al., 1999
; Welt et al., 1999
). E2 secretion decreases later during ovarian ageing. The patients in our studies, especially in study B, may represent different stages of ovarian ageing. Hence, E2 response to FSH is useless as a marker for ovarian response in this heterogeneous group of patients.
Our study is the first to determine serial changes in serum inhibins throughout FSH treatment in normal and low responders. In agreement with previous pharmacodynamic studies (le Contonnec et al., 1994), we found that serum FSH level after daily administration at either of two fixed doses (300 or 600 IU) resulted in stable serum FSH concentrations from day 35. In our previous study and those of others, on patients with normal ovarian response (Lockwood et al., 1998
; Eldar-Geva et al., 2000
), the maximal inhibin B response was observed 23 days later. The current study shows that in patients with low ovarian response (study B), serum inhibin B concentrations stabilized earlier, even before FSH achieved its maximal levels (Figure 3
). Patients with very low oocyte number had almost no change in serum inhibin B levels throughout treatment. In contrast, in patients with normal ovarian response (study A) the time course of inhibin B was similar to the course of FSH. This difference may represent suboptimal inhibin B secretion from small and medium size follicles in the patients from study B. Another possibility is that recruitment of follicles continues beyond the first days of FSH stimulation in the patients from study A, but not in study B.
In conclusion, serum inhibin B levels determined during the early stages (e.g. after two or three daily doses) of FSH treatment provide an early indication of the number of recruited follicles which are destined to form mature oocytes and indicates those patients in whom a reasonable response will be achieved and sufficient oocytes will be retrieved. It seems that serum inhibin B is a better predictor of the number of oocytes retrieved than serum E2 or inhibin A levels. Both the patients and the clinician may use this information in making decisions regarding cancellation of a cycle or, perhaps, modulating the FSH or the GnRH agonist doses.
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Acknowledgements |
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Notes |
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References |
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Submitted on January 17, 2002; resubmitted on March 21, 2002; accepted on May 16, 2002.