Objective: To investigate serum and follicular fluid insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) behavior in spontaneous and in superstimulated cycles.
Design: Estradiol, GH, IGF-I, and IGFBP-3 were evaluated in serum and in follicular fluid during spontaneous and stimulated cycles.
Setting: Department of Obstetrics and Gynecology, University of Naples, Naples, Italy.
Patient(s): Ninety-two patients with regular menstrual cycles and tubal and/or male factor infertility undergoing treatment with an IVF program.
Intervention(s): The superstimulated IVF program uses leuprolide acetate suppression followed by hMG in a sequential manner in the subsequent cycle. After sufficient follicular development, hCG was administered, followed 34-36 hours later by oocyte retrieval.
Main outcome measure(s): Growth hormone, IGF-I, and IGFBP-3 were assayed by RIA and immunoradiometric assay techniques.
Result(s): Growth hormone levels in serum and in follicular fluid were higher after FSH-stimulated cycles than after physiologic cycles. Serum and follicular fluid IGF-I did not change during physiologic and FSH-stimulated cycles. Serum IGFBP-3 decreased only in FSH-stimulated cycles. Levels of IGFBP-3 in follicular fluid were lower than serum levels in late follicular phase both in physiologic and in FSH-stimulated cycles.
Conclusion(s): Reduction of IGFBP-3 is an important mechanism allowing a larger local availability of free IGFs, which modulate the response of follicles to gonadotropin stimulation. This effect is amplified in stimulated cycles.