Impaired metoclopramide-induced pituitary prolactin release in men with human immunodeficiency virus infection

To investigate whether metoclopramide-induced prolactin release is impaired in HIV-infected men, we studied 10 clinically healthy HIV-negative adult men (group 1) and 10 consecutive HIV-positive adult men (group 2) with anti-HIV antibodies confirmed by Western blot analysis and a CD4 cell count from 13 to 570x10(6)/L. After a 10- to 12-hour overnight fast, three basal blood samples were obtained at 15-minute intervals (-30, -15, and 0 minutes) and thereafter at 15, 30, 60, 90, 120, 180, and 240 minutes after a 10-mg intravenous bolus of metoclopramide. Duplicate serum prolactin concentrations were measured in each sample with commercially available radioimmunoassay kits. No significant differences between groups were observed in basal prolactin levels. Group 2 had lower serum prolactin concentrations than group 1 throughout the test (P< or =.002). The area under the prolactin curve (mean +/- SD) was also lower in group 2 than in group 1 (7156+/-1433 ng/mL/240 min vs. 12430+/-2454 ng/mL/240 min, P<.0001), and the area under the prolactin curve had a significant correlation with the CD4 cell counts (r = 0.7912, P<.001). These findings suggest that the hypothalamic dopaminergic tone, although present, was clearly diminished in these HIV-positive men regardless of their clinical stage.