GnRH agonist versus antagonist therapy

J.A. Garcia-Velasco2,1 and A. Pellicer2

2 IVI–Madrid C/ Santiago de Compostela 88, 28035 Madrid, Spain


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 Introduction
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Dear Sir,

We thank the interest of Dr Al-Inany in our recent publication (Garcia-Velasco et al., 2001Go), but most of his concerns are clearly expressed in our manuscript. As stated in the title and discussed throughout the manuscript, the study of main interest was to test if there is any difference in human ovarian steroid secretion in vivo in IVF patients treated either with GnRH agonist or antagonist. Thus, we are dealing with an experimental setting where the main endpoint is to compare steroid concentration in follicular fluids and sera from IVF patients who have been previously treated with these two drugs, but not their clinical outcome. As stated in the Abstract and in the last paragraph of the Discussion, we reached a clear-cut conclusion, as a significant effect on ovarian follicular steroidogenesis was observed in women undergoing GnRH antagonist therapy. Secondary endpoints were several parameters of the ovarian stimulation, but the study was not designed to compare clinical outcome, as it was experimental data obtained from clinical patients undergoing a phase III, prospective, non-randomized clinical trial (Pocock, 1975).

There are already several well-designed, properly conducted clinical trials where their primary endpoint was the clinical outcome using the same GnRH antagonist we used (cetrotide) (Albano et al., 2000Go; Olivennes et al., 2000Go), but this was not our purpose, as explained in the Introduction section of the manuscript. Individual variation in the duration of the down-regulation period as well as different length of the stimulation period explains the differences between GnRH agonist mean total dose and mean number of days.


    Notes
 
1 To whom correspondence should be addressed.

E-mail: jgvelasco{at}ivi.es Back


    References
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 Introduction
 References
 
Albano, C., Felberbaum, R.E., Smitz, J., Riethmuller-Winzen, H., Engel, J., Diedrich, K. and Devroey, P. (2000) Ovarian stimulation with HMG: results of a prospective randomized phase III European study comparing the luteinizing hormone-releasing hormone (LHRH)-antagonist cetrorelix and the LHRH-agonist buserelin. European Cetrorelix Study Group. Hum. Reprod., 15, 526–521.[Abstract/Free Full Text]

Garcia-Velasco, J.A., Isaza, V., Vidal, C., Landazábal, A., Remohí, J., Simón, C. and Pellicer, A. (2001) Human ovarian steroid secretion in vivo: effects of GnRH agonist versus antagonist (cetrorelix). Hum. Reprod., 16, 2533–2539.[Abstract/Free Full Text]

Olivennes, F., Belaisch-Allart, J., Emperaire, J.C., Dechaud, H., Alvarez, S., Moreau, L., Nicollet, B., Zorn, J.R., Bouchard, P. and Frydman, R. (2000) Prospective, randomized, controlled study of in vitro fertilization–embryo transfer with a single dose of a luteinizing hormone-releasing hormone (LH-RH) antagonist (cetrorelix) or a depot formula of an LH-RH agonist (triptorelin). Fertil. Steril., 73, 314–320.[ISI][Medline]

Pocock, S.J. (1984) Clinical Trials: a Practical Approach. Wiley, New York, USA, pp. 266.





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