Age-related changes in the metoclopramide-induced prolactin release in nulliparous women

Objective To assess the metoclopramide-stimulated PRL response in nulliparous women as a function of chronological age (CA). Design Open and prospective study. Setting Outpatient endocrine clinic of a third level medical institution. Patients Fifty-one clinically healthy volunteer nulliparous women 15.8 to 48.2years of age, with regular menses at least 1year before the study (except 3 postmenopausal women) and no regular drug ingestion during the last 6months, studied on days 18 to 22 of their menstrual cycle. Interventions After a 30-minute rest, three basal blood samples were obtained; oral metoclopramide (10mg) was administered followed by subsequent blood samples at 60, 90, and 120minutes. Main Outcome Measures Duplicate serum PRL determinations were performed by RIA in all samples with P and E 2 only in the pool of the basal samples. Hypothesis was formulated before data collection. Results All menstruating women had serum P levels≥4.0ng/mL (≥12.72nmol/L). A linear correlation was observed between CA and the serum PRL response, and also between CA and serum E 2 . Multiple regression analysis showed that CA and body mass index had the most marked effect on PRL response. Women≤25.0years old had a serum PRL response and mean basal serum E 2 levels lower than women>25.1years old. Conclusions The metoclopramide-induced PRL response in nulliparous women augmented linearly as CA increased, suggesting a gradual decrease in the dopaminergic tone in older women, perhaps partially compensated by a high estrogen level to prevent an unrestrained rise in serum PRL levels.