Institut Clinic of Gynecology, Obstetrics and Neonatology, Hospital Clínic-IDIBAPS, Faculty of Medicine, University of Barcelona, C/Casanova 143, 08036-Barcelona, Spain
Correspondence: E-mail: jbalasch{at}medicina.ub.es
Dear Sir,
Thank you very much for giving me the opportunity to reply Dr Filicori's letter regarding our paper (Balasch et al., 2001) and to clarify several issues that he seems to have misunderstood and thus may be misleading to the reader of the letter. His main concern is our conclusion stressing that there is no need for additional exogenous LH supplementation in down-regulated women receiving a recombinant FSH-only preparation. Let me now respond to the points raised by Dr Filicori in his opposition to that conclusion:
(1) Dr Filicori's first point emphasises that low mid-follicular phase LH concentrations have been associated with a longer duration of stimulation, lower rates of oocyte and embryo yield, higher incidence of poor response (Fleming et al., 2000), and increased early pregnancy wastage (Westergaard et al., 2000
). Fleming's report includes two consecutive time frames of study in which the gonadotrophin used was either purified urinary FSH (first study) or recombinant human FSH (second study). In none of the above outcome variables were there differences between `low LH' and `normal LH' patients when ovarian stimulation was performed with Gonal-F (the same recombinant FSH preparation used in our study). Therefore, the study by Fleming et al. clearly supports rather than contradicts our results (Fleming et al., 2000
). Similarly, again using Gonal-F, Westergaard et al. found that women with `low' LH concentrations, `Were comparable with the normal LH group with regard to the variables characterizing the stimulation protocol with the exception of serum estradiol concentration' (Westergaard et al., 2000
). However, in the study by Westergaard et al. a five-fold higher risk of early pregnancy loss was found in the low LH group. Interestingly, the overall early pregnancy loss rate in that study was 25%. This rate is completely consistent with rates observed in large databases of outcomes with assisted reproduction (Society for Assisted Reproductive Technology and American Society for Reproductive Medicine, 2000
). Therefore, if the LH suppression postulate of Filicori is valid, it would be the explanation (cause) for most (all) early pregnancy losses after IVF/ICSI treatment irrespective of gonadotrophin used. Obviously, this premise can hardly be true. Again, the study by Fleming et al. is in agreement with ours when stressing that, `There was no difference in the rate of early pregnancy loss in the patients, irrespective of ovarian stimulant used or the circulating LH' (Fleming et al., 2000
).
(2) Dr Filicori again may confuse the reader by indicating that case selection criteria in the Fleming and Westergaard studies were markedly different from those in our report. Curiously, all three studies used the same study design: blood samples stored prospectively and assayed retrospectively. We collated the data from a cohort of women having a positive pregnancy test in order to compare mid-follicular LH levels in ongoing pregnancies versus early pregnancy losses, as did Fleming and Westergaard. In addition, we matched conception ART cycles with non-conception ART cycles in order to present new information when comparing both group of patients with respect to mid-follicular LH levels. It is noteworthy that in both previous studies (Fleming et al., 2000; Westergaard et al., 2000
) the threshold values for LH were established according to the detection limit of LH assays used, whereas in our study we used a statistical method involving receiver operating characteristic curve analysis to test the usefulness of mid-follicular LH concentration as a test to discriminate between ongoing pregnancies and early pregnancy losses and also between conception and non-conception cycles. Considering both the sensitivity and coefficients of variation of the assays used to measure serum LH, it is unlikely that methodological differences in the different assays would account for lack of agreement among those studies.
(3) We agree with Dr Filicori that discrepancies between previous studies and ours with respect to ovarian steroidogenesis could be explained on the basis of the GnRH agonist used. If the agonist is an effect modifier, then studies should be focused on trying to identify the optimal agonist. However, we disagree with Dr Filicori's assertion that LH activity supplementation is needed on the basis that, `Low follicular phase estradiol levels is one of the potential mechanisms by which inadequate LH input may exert untoward effects on oocyte and embryo quality'. There is no evidence from the studies of Fleming, Westergaard or Balasch to support this claim (see above). In fact, the lesser relevance, if any, of estrogens in follicular development in the primate ovary is well supported by studies in women with congenital abnormalities of estrogen synthesis due to mutated steroidogenic enzymes in whom follicular maturation, fertilization and even implantation have been achieved (Rabinovici et al., 1989; Pellicer et al., 1991
, 1992
). Finally, the amount of LH activity actually necessary for normal follicle and oocyte development is not known, but is likely to be very low, since <1% of follicular LH receptors need to be occupied in order to allow normal steroidogenesis (Chappel and Howles, 1991
; Le'vy et al., 2000
). Thus, the amount of residual endogenous LH remaining during full-dose GnRH agonist pituitary suppression is certainly sufficient in most women to achieve adequate follicular maturation during ovarian stimulation with FSH-only drugs. In fact, the switch in stimulation regimens to a more widespread use of FSH-only preparations, without LH supplementation, has been associated with an increased rate of overall programme success (FIVNAT, 1999
, 2000
); a decrease would have been expected if Filicori's hypothesis was correct.
(4) The final part of the letter where Dr Filicori emphasises that patients will universally profit from LH activity supplementation during FSH ovulation induction is surprising considering one of his previous studies (Filicori et al., 1996) analysing the endocrine mechanisms underlying the outcome of different ovulation induction regimens with gonadotrophins and GnRH agonists. From that study, the authors concluded that, `The presence of LH in exogenous gonadotrophin preparations only appeared to affect marginally serum or follicular fluid hormone levels and folliculogenesis, although there seems to be a trend toward an enhanced follicle yield when purified FSH is used'.
This part of the letter is again confusing considering that, to support his contention, Dr Filicori is mixing papers where World Health Organization group I anovulatory patients were treated with recombinant FSH associated with recombinant LH (The European Recombinant Human LH Study Group, 1998) or urinary FSH plus HCG (Filicori et al., 1999a
) for ovulation induction, and reports dealing with ovarian stimulation under pituitary suppression in normally ovulating women treated with FSH plus HCG or HMG (containing variable amounts of HCG) for ovulation induction alone or associated with intrauterine insemination (Filicori et al., 1999b
, 2001
). Countering Dr Filicori's position, the following points should be noted: (i) the best and only true model to correctly investigate any LH hypothesis is the hipogonadotrophic woman who may be totally LH deficient in contrast with down-regulated women where LH is not absent; (ii) HCG is a hormone designed to support pregnancy not estrogen biosynthesis in the follicular phase; (iii) HCG is not normally present in normal fertile women during this period; (iv) LH over millions of years has evolved to produce a signal which can be rapidly switched on or off; (v) there are no data to support the notion that HCG represents the most important LH activity in vivo; (vi) No conclusion can be drawn from those studies (including only non-IVF patients) with respect to oocyte quality, fertilization rate and embryo yield. In contrast, in two large comparative studies comparing pure or highly purified FSH versus HMG in an IVF programme, we reported that HMG use did not improve folliculogenesis or oocyte yield (Balasch et al., 1996
). The same result was observed in the report by Gordon et al. quoted by Dr Filicori to support his contention that LH activity contained in HMG could improve embryo implantation (Gordon et al., 2001
). Gordon et al. used preparations containing 0, 1, 25 and 75 IU LH respectively. The sample size was small and randomization led to differences of >25% in the number of patients assigned to the groups. Live birth rates were not different in the four groups studied and the trend in implantation rates with increasing LH dosage was non-linear. If Filicori's postulate was true, a linear dose-dependent finding would be expected. It does not make biological sense that implantation rates with 0, 25 and 75 IU LH were similar but much lower with 1 IU LH. In addition, Gordon et al. used trend analysis for their data but the unit of randomization in their trial was the patient and not the embryo (Gordon et al., 2001
); therefore, the trend analysis on the implantation rate which pertains to embryos transferred was used incorrectly. Finally, Dr Filicori suggested that the additional LH activity can reduce small preovulatory antral follicle number and thus the risk of ovarian hyperstimulation syndrome (Filicori et al., 2001
). Detailed studies clearly showed that both a decrease in the fraction of the mature follicles and an increase in the fractions of the intermediate and the very small follicles is correlated with an augmented risk for the development of the syndrome (Blankstein et al., 1987
). Thus, if LH activity could really improve folliculogenesis, a higher oocyte yield with the use of HMG versus FSH-only drugs in IVF should be expected; certainly, this was never proved.
Finally, we agree with Dr Filicori that prospective studies are useful to test the hypothesis that LH addition is efficacious. However, given the evidence available so far, there is no need for randomized clinical trials because addition of LH does not seem necessary. The point, therefore, is moot.
References
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