The extracerebral dopamine antagonist domperidone block the suppressive effect of bromocriptine on prolactin and TSH secretion in man.

The effects of a single oral dose of 2.5 mg bromocriptine on serum level of TSH and prolactin were studied in a group of normal male subjects. Bromocriptine effectively inhibited basal TSH and prolactin concentration as well as the prolactin and TSH response to TRH given 4 hours later. The prior administration of the extracerebral dopamine antagonist domperidone reversed the endocrine effects of bromocriptine. The results suggest that dopamine receptors located at the pituitary may regulate TSH (and prolactin) release in man.