Blockage of ghrelin-induced prolactin secretion in women by bromocriptine

ObjectiveTo investigate the effect of bromocriptine on ghrelin-induced PRL secretion in women.DesignLongitudinal study.SettingUniversity hospital.Patient(s)Ten healthy, normally cycling women.Intervention(s)The women were injected IV on day 3 of three cycles with a single dose of normal saline (cycle 1) or ghrelin (1 μg/kg) after pretreatment for 2 days either with placebo (cycle 2) or with bromocriptine (cycle 3) per os. Blood samples were taken before and frequently after drugs administration for 120 minutes.Main Outcome Measure(s)The PRL and GH responses to ghrelin were assessed.Result(s)Bromocriptine suppressed basal PRL levels significantly. The injection of ghrelin stimulated a significant increase in serum PRL levels in cycle 2 but not in cycle 3, in which PRL levels remained stable. The response of GH to gherlin was significantly attenuated in cycle 3 as compared with cycle 2.Conclusion(s)The present study demonstrates for the first time that bromocriptine blocked the stimulating effect of ghrelin on PRL release and attenuated the GH response to the same stimulus. The mechanism of these interactions needs to be clarified.