Comparison of LH concentrations in the early and midluteal phase in IVF cycles after treatment with HMG alone or in association with the GnRH antagonist Cetrorelix

Luteinizing hormone (LH) is mandatory for the maintenance of the corpus lut eum, Ovarian stimulation for IVF has been associated with a defective lutea l phase. The luteal phases of two groups of patients with normal menstrual cycles and no endocrinological cause of infertility were retrospectively an alysed in IVF cycles. Thirty-one infertile patients stimulated with human m enopausal gonadotrophins (HMG) for IVF to whom the gonadotrophin-releasing hormone (GnRH) antagonist Cetrorelix 0.25 mg was also administered to preve nt the LH surge (group I) were compared with 31 infertile patients stimulat ed with HMG alone (group II). Despite differences in the stimulation outcom e, luteal LH serum concentrations were similar in the two groups. LH values dropped from 2.3 +/- 1 IU/l on the day of human chorionic gonadotrophin (H CG) administration to 1.1 +/- 0.7 IU/l on day HCG +2 in group I (P < 0.0001 ) and from 5.1 <plus/minus> 3 to 1.2 +/- 1.7 IU/l (P < 0.0001) in group II. In the mid-luteal phase, LH concentrations were low in both groups. Our re sults suggest that suppressed LH concentrations in the early and mid-luteal phase may not be attributed solely to the GnRH-antagonist administration. Pituitary LH secretion may be inhibited by supraphysiological steroid serum concentrations via long-loop feedback and/or by the central action of the exogenously administered HCG via a short-loop mechanism.