Inhibin B predicts oocyte number and the ratio IGF-I/IGFBP-1 may indicate oocyte quality during ovarian hyperstimulation for in vitro fertilization

To perform a retrospective analysis of 62 age-matched IVF-treated women in order to investigate whether levels of inhibin B, IGF-I, and IGFBP-1 in serum 2 days before oocyte retrieval and in follicular fluid at the day of oocyte retrieval might be useful as indicators of the ovarian ability to produce oocytes (ovarian reserve). Patients were allocated into three groups on the basis of the number of oocytes retrieved. Group 1 ("low responders") had 0-3 oocytes, group 2 ("normal responders") had 6-11 oocytes, and group 3 ("high responders") had 12 oocytes or more. Levels of inhibin B, IGF-I, and IGFBP-1 in follicular fluid and in serum obtained 2 days before oocyte retrieval were analyzed and correlated to clinical parameters including estradiol levels, progesterone levels, follicle size, follicle number, and oocyte number. We found significant differences in inhibin B levels in the three groups. Inhibin B levels in follicular fluid and serum was strongly correlated to the number of oocytes retrieved (p < 0.01). The number of oocytes retrieved were also correlated to total FSH dose (p < 0.05), to estradiol 2 days before and at ovum pick-up (p < 0.05), to progesterone at ovum pick-up (p < 0.0001), to progesterone at embryo transfer (p < 0.05), and to the number of follicles (size 12-15 mm, p < 0.001, size > 15 mm, p < 0.01). Serum inhibin B also correlated to follicular fluid inhibin B (p < 0.01). Inhibin B was not correlated to pregnancy. In contrast, the ratio IGF-I/IGFBP-1 in serum as well as in follicular fluid was significantly higher in women who became pregnant (p < 0.05). The results show that inhibin B in serum 2 days before oocyte retrieval predicts number of oocytes retrieved. Since inhibin B in serum before oocyte retrieval in ovarian hyperstimulation was strongly predictive of the number of oocytes retrieved, it appears useful as a marker for ovarian response. Inhibin B did not predict treatment outcome, whereas the ratio IGF-I/IGFBP-1 in serum and follicular fluid was significantly higher in women who became pregnant. The ratio IGF-I/IGFBP-1 may thus reflect oocyte quality.