In a previous study we demonstrated that women with day 3 luteinizing hormone (LH) values < 3 IU/l subjected to controlled ovarian hyperstimulation without pituitary desensitization responded with a lower number of follicles > 15 mm compared to women with a higher basal LH level. The aim of this study was to determine whether in patients with day 3 LH levels < 3 IU/l a further reduction of serum LH concentration by gonadotropin-releasing hormone (GnRH) analog impairs follicular response to follicle stimulating hormone (FSH) and treatment outcome in in vitro fertilization (IVF) cycles. For this purpose we retrospectively studied 249 consecutive women subjected to standard IVF treatment employing pituitary desensitization with buserelin and follicular stimulation with urinary highly purified FSH. The patients were divided into two groups according to their day 3 LH value. The first group (group A) showed day 3 LH levels < 3 IU/l and the second (group B) had day 3 LH levels > 3 IU/l. Group A and B patients did not show statistically significant differences in the ovarian response to FSH, nor in IVF treatment outcome, showing that in FSH treated GnRH analog suppressed cycles, the ovarian responsiveness and IVF outcome do not differ according to basal LH values. However, the high dosage of FSH we employed in group A and B patients could account, at least in part, for this result. Indeed, comparative evaluations with unsuppressed cycles (our previous study) strongly suggest that a reduced ovarian responsiveness to gonadotropins in patients with day 3 LH values < 3 IU/l should be considered in clinical practice.