Differential prolactin response to oral metoclopramide in nulliparous versus parous women throughout the menstrual cycle

Abstract

To analyze if serum prolactin (PRL) changed throughout the menstrual cycle and if parous women have lower PRL than nulliparous women. A prospective study of PRL was performed in basal conditions and during oral metoclopramide stimulation on days 7, 14, and 21 of menstrual cycle. Instituto Nacional de Perinatología, third level medical institution. Four parous (group A) and seven nulliparous (group B) healthy volunteer women entered and finished the study. Women were studied each day before and every 30 minutes during 2 hours after oral metoclopramide (10 mg). Duplicate PRL determinations were performed by radioimmunoanalysis. Hypothesis was formulated before data collection. Group A and B had similar basal PRL levels and no within group differences existed in response to metoclopramide, regardless of the day studied. Group A had lower PRL increments than group B from 60 to 120 minutes on days 14 and 21 (P less than 0.05); the peak increments also were lower on days 7, 14, and 21 (P less than 0.05). Parous women had a diminished PRL response. Although the dopaminergic tone was similar throughout the menstrual cycle within each group, two distinct levels of dopaminergic tone existed in parous and nulliparous women.