Paracrine interactions among insulin-like growth factor-I, insulin-like growth factor binding protein-1, and steroid hormones in follicular fluid

Objective-To improve understanding of follicular paracrine interactions. Patients and Methods-The levels of insulin-like growth factor I (IGF-I) and the IGF-binding protein-1 (hIGFBP-1) in 28 follicular fluid samples obtained from 10 in vitro fertilization patients were measured. Only samples containing mature oocytes which subsequently fertilized and cleaved were studied. These levels were then related to follicular fluid steroid levels in the individual follicle, pregnancy outcome, and the use of leuprolide acetate. Results-Linear regression analysis demonstrated a positive relationship between individual follicular fluid levels of IGF-I and hIGFBP- 1, as well as between levels of estradiol and hIGFBP-1. There was a negative relationship between follicular fluid progesterone/estradiol ratios and the levels of both IGF-I and hIGFBP-1. Mean follicular fluid levels of IGF-I and hIGFBP-1 were not statistically related to pregnancy outcome or leuprolide use. Lower mean follicular fluid levels of estradiol and consequently higher follicular fluid progesterone/estradiol ratios were found among patients who achieved pregnancy compared to nonpregnant patients. Conclusion-Our results support the concept that critical interactions involving IGF-1, hIGFBP-1, and steroid hormones are necessary for the maintenance of an intrafollicular milieu favorable for optimal oocyte development.