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

Abstract

To assess the metoclopramide-stimulated PRL response in nulliparous women as a function of chronological age (CA). Open and prospective study. Outpatient endocrine clinic of a third level medical institution. Fifty-one clinically healthy volunteer nulliparous women 15.8 to 48.2 years of age, with regular menses at least 1 year before the study (except 3 postmenopausal women) and no regular drug ingestion during the last 6 months, studied on days 18 to 22 of their menstrual cycle. After a 30-minute rest, three basal blood samples were obtained; oral metoclopramide (10 mg) was administered followed by subsequent blood samples at 60, 90, and 120 minutes. Duplicate serum PRL determinations were performed by RIA in all samples with P and E2 only in the pool of the basal samples. Hypothesis was formulated before data collection. All menstruating women had serum P levels > or = 4.0 ng/mL (> or = 12.72 nmol/L). A linear correlation was observed between CA and the serum PRL response, and also between CA and serum E2. Multiple regression analysis showed that CA and body mass index had the most marked effect on PRL response. Women < or = 25.0 years old had a serum PRL response and mean basal serum E2 levels lower than women > 25.1 years old. 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.