Subtle progesterone rise after the administration of the gonadotrophin-releasing hormone antagonist cetrorelix in intracytoplasmic sperm injection cycles.

In the present study, subtle serum progesterone rise (>= 1.1 ng/ml) during the late follicular phase is reported, for the first time to our knowledge, in patients using a potent gonadotrophin-releasing hormone (GnRH) antagonist, Cetrorelix, in combination with human menopausal gonadotrophin (HMG) for ovarian stimulation prior to intracytoplasmic sperm injection (ICSI). In five out of 24 patients (20%) serum progesterone levels were >/= 1.1 ng/ml. The cycle characteristics of the patients were similar in both groups. No premature endogenous luteinizing hormone (LH) surge occurred and the serum LH concentrations were constantly low during the follicular phase. The 17-beta oestradiol and follicle stimulating hormone (FSH) exposure were higher in cycles with premature luteinization. The greater oestradiol and FSH exposure confirm that one of the possible factors inducing subtle serum progesterone rise is the increased oestradiol and FSH-induced LH receptivity in granulosa cells.