Prolactin secretion in idiopathic hypogonadotropic hypogonadism during pulsatile luteinizing hormone-releasing hormone long-term administration

Recent data seem to suggest that LHRH may be involved in the modulation of PRL secretion. We studied the PRL pattern in 9 males (age range 18–38 yr) with idiopathic hypogonadotropic hypogonadism (IHH) before and during long-term pulsatile LHRH therapy (120–160 ng/kg bw every 120 min sc) in order to evaluate variations in the spontaneous PRL secretion or LHRH-induced presence of PRL pulse. LH, FSH and PRL secretion was evaluated every 15 min for 3 h on day 0, day 30 and days 90–150. Before and during LHRH therapy PRL 24-h integrated concentration (IC) and gonadotropin or PRL response to LHRH test (50 μg iv/bolus) were evaluated. On day 0 spontaneous PRL pulses were found in 2 IHH patients. On day 30 PRL pulses were found in 4 cases. On days 30–90 PRL pulses were sporadically concomitant with LHRH-induced LH pulses. Mean PRL levels and 24-h IC of PRL were found to be significantly (p < 0.05) increased during pulsatile LHRH administration. A significant positive (p < 0.01) correlation was observed between testosterone and PRL levels during LHRH therapy. When compared to a significant LH response to LHRH iv bolus, no modification of PRL secretion was found. The present study did not show any relationship between LHRH administration and PRL secretion. It might be hypothesized that LHRH does not play a determinant role in PRL secretion and does not seem to modulate PRL secretory pattern in IHH males.