Preserved pituitary response under ovarian stimulation with HMG and GnRH antagonists (Cetrorelix) in women with tubal infertility

Objective: To examine the pituitary response in patients undergoing short-term application of the GnRH antagonist Cetrorelix in the mid-cycle phase for hypophysial suppression of premature LH surges within an IVF-program. Design: Twenty patients suffering from primary or secondary tubal infertillty were stimulated with hMG from cycle day 2. From day 7 till ovulation induction Cetrorelix was administered in two different dose regimens (15 patients 3 mg s.c. daily; 5 patients 1 mg s.c. daily). Three hours before ovulation induction a GnRH test was performed using 25 μg of native GnRH and the pituitary response examined by measurement of the serum LH concentration after 30 min. Results: Premature LH surges could be avoided in the 3-mg group and in the 1-mg group, respectively. Due to this, none of the cycles had to be cancelled. Oestradiol profiles and ultrasound demonstrated a satisfactory follicular maturation. All patients showed pronounced suppression of the serum LH levels before ovulation induction. The mean increase of serum LH due to the performed GnRH test was 10 mIU/ml for the 3-mg group, while the average maximum in the 1-mg group was about 32.5 mIU/ml. Conclusions: The pituitary response is preserved by the treatment with the GnRH antagonist Cetrorelix. The extent of suppression of the adenohypophysis, as expressed by the different reactions on GnRH test, can be modulated by the dosage administered. This should allow ovulation induction by GnRH or one of its agonists instead of hCG, which could be beneficial in patients at high risk of Ovarian Hyperstimulation Syndrome (OHSS) and those suffering from Polycystic Ovary Disease (PCOD).