Does plasma insulin level affect ovarian response to exogenous administration of follicle-stimulating hormone in women without polycystic ovary syndrome?

Background. Raised insulin levels have been shown to contribute to ovarian overproduction of androgens. Hyperinsulinemia, usually associated with polycystic ovary syndrome (PCOS), brings about greater ovarian endocrine and morphological responses to ovulation induced by follicle-stimulating hormone (FSH). This indicates that elevated levels of insulin play a role in the endocrine and paracrine control of the ovaries. Objective. The aim of the present study was to investigate whether basal insulin levels influence ovarian response to FSH in healthy women (non-PCOS) undergoing assisted reproduction by in vitro fertilization-embryo transfer (IVF-ET). Methods. The study included 36 consecutive women, 27-45 years old, undergoing IVF-ET for tubal-factor or male-factor infertility. Serum insulin levels were determined on the day of administration of gonaclotropin-releasing hormone analog (GnRHa) and on the first day of FSH administration. Results. Mean insulin levels were 6 +/- 3 and 7 +/- 3 mu U/ml on the day of GnRHa and FSH administration, respectively. No correlations were found between basal insulin level, days of treatment, total FSH dose, estradiol level and the number of oocytes retrieved. Conclusions. The results of the present study show that normal levels of insulin do not seem to influence ovarian response to FSH in non-PCOS women. In all patients included in our study, serum insulin levels did not correlate with IVF stimulation data (days of stimulation, total FSH dose) nor with IVF-ET outcome. Thus the study demonstrates that, in patients who are not insulin-resistant, insulin does not correlate with ovarian response to FSH administration.