Submaximal plasma prolactin response to TRH and dopamine activity in man

Submaximal plasma prolactin responses to TRH were evaluated as a measure of endogenous dopamine activity in man. In 25 male subjects, plasma prolactin responses to 0.5 mg i.m. haloperidol were significantly correlated with plasma prolactin responses to 12.5 micrograms i.v. TRH but not with plasma prolactin responses to 200 micrograms i.v. TRH or with basal plasma prolactin levels. The results suggest that submaximal plasma prolactin responses to TRH may reflect the effects of endogenous dopamine activity on prolactin release more accurately than the prolactin measures previously used.