The effect of apomorphine on basal and TRH stimulated release of thyrotrophin and prolactin in man.

Studies were performed in two groups of healthy male volunteers to evaluate the effect of apomorphine on the secretion of thyrotrophin (TSH) and prolactin under basal conditions and following the administration of thyrotrophin releasing hormone (TRH). Apomorphine HCl, administered sc in a dose of 0.75 mg had no effect on the basal levels of plasma TSH or serum prolactin. The iv injection of 200 mug TRH was followed by an increase in TSH and prolactin in all subjects, with a maximum 20-30 min after the injection. When 0.75 mg of apomorphine was injected sc 30 min before TRH, the increase in prolactin was significantly reduced whereas the TSH response was unaltered. Our studies indicate that the TRH induced secretion of prolactin in man can be suppressed through a dopaminergic mechanism whereas the secretion of TSH is not influenced.