Metoclopramide stimulates prolactin secretion in man

Area of Science:

• Endocrinology
• Neuropharmacology

Background:

• Metoclopramide is a widely used medication with known effects on the gastrointestinal and central nervous systems.
• Its influence on endocrine function, particularly prolactin secretion, requires further elucidation.

Purpose of the Study:

• To investigate the effect of metoclopramide on serum prolactin concentrations in adult men.
• To explore the potential mechanisms underlying metoclopramide-induced prolactin elevation.

Main Methods:

• Administration of 10 mg metoclopramide orally or intravenously to adult men.
• Measurement of serum prolactin levels at various time points post-administration.
• Evaluation of the effects of bethanechol, atropine, and L-dopa on metoclopramide-induced prolactin changes.

Main Results:

• Oral or intravenous metoclopramide administration resulted in a significant approximate sixfold increase in serum prolactin.
• Elevated prolactin levels persisted for up to 9 hours after oral and 2 hours after intravenous metoclopramide.
• L-dopa pre-treatment inhibited the early prolactin increase, suggesting a role for dopamine.
• Bethanechol did not affect prolactin levels, and atropine did not inhibit the metoclopramide effect.

Conclusions:

• Metoclopramide is a potent stimulator of prolactin release in adult men.
• The prolactin-elevating effect appears to be mediated by the inhibition of dopamine, likely through hypothalamic pathways.
• Metoclopramide may serve as a valuable tool in clinical investigations of hypothalamic-pituitary function.