Serum concentrations of PRL, LH and FSH were examined in 17 perimenopausal women with dysfunctional uterine bleeding (PDUB group), after stimulation with exogenous GnRH (a 100-μg i.v. bolus dose), and endogenous GnRH (as induced by an estrogen challenge test). Five normal cycling women during the follicular phase of the cycle were used as control (FP group). Exogenous GnRH induced increments in the concentration of PRL, FSH and LH in PDUB and FP women. Increases were statistically higher for FSH (p < 0.001) and LH (p < 0.01), but not for PRL, in the FP group. No significant correlation was found between LH-PRL or FSH-PRL in PDUB women. A positive correlation was found when the maximal LH percent change for each case was compared with the simultaneous PRL percent value (r = 0.83, p < 0.001) during the estrogen test. We conclude that, as shown by previous studies in both hypogonadal and normal women, also in this perimenopausal model exogenous GnRH induces secretion of PRL, LH and FSH, and that a positive correlation exists between LH and PRL under the finely modulated stimulation of gonadotrophs by endogenous GnRH.