FREQUENCY OF PROLACTIN PULSATILE RELEASE IN NORMAL MEN AND IN AGONADAL PATIENTS IS NEITHER COUPLED TO LH-RELEASE NOR INFLUENCED BY ANDROGEN MODULATION

OBJECTIVE We wished to examine and characterize the prolactin pulsatile secretory pattern in both normal and agonadal males in order to assess whether there was any concordance with LH secretion. DESIGN Patients were sampled every 5 minutes for 12 hours. PATIENTS We studied five normal and four agonadal men, the latter group before and on testosterone enanthate (TE) (200 mg i.m. every 15 days) treatment. MEASUREMENTS Prolactin and luteinizing hormone plasma levels were determined using commercial RIA systems. Pulse detection was performed using the DETECT program and the degree of concordance between luteinizing hormone and prolactin was established computing the specific concordance index. RESULTS We demonstrated the presence of a frequent PRL secretory pattern in normal men (22.8 +/- 1.8 peaks/12h; mean +/0 SEM) and in agonadal patients, both in basal conditions and during testosterone treatment (20.5 +/- 2.8 and 18 +/- 1.6 peaks/12h, respectively). The testosterone treatment in agonadal men significantly reduced luteinizing hormone pulse frequency (baseline: 27.5 +/- 2, testosterone administration: 18 +/- 1.3 peaks/12h, P < 0.01) but did not affect pulsatile prolactin release. Using a 10 and 15 minute sampling protocol, we observed that prolactin pulse frequency significantly decreased (P < 0.01) and was similar to the frequencies estimated in previous reports. When luteinizing hormone and prolactin time series were studied to evaluate the possible presence of a specific concordance (SC) between the secretory events of the two hormones, no significant degree of concomitancy was observed neither using the specific concordance index or the cross-correlation analysis. CONCLUSONS This report demonstrates (a) the presence of frequent pulsatile release of prolactin in both controls and agonadal patients (baseline and on testosterone enanthate), (b) the use of an appropriate sampling interval (5 minutes) to unmask the prolactin pulsatile release, (c) that in men, luteinizing hormone secretory events are not temporally linked to prolactin secretion, and (d) that androgens, even if reducing luteinizing hormone pulse frequency in agonadal patients, do not significantly affect prolactin pulsatile secretion, suggesting that testosterone and its metabolites do not affect lactotroph activity.