Plasma prolactin response to submaximal stimulation by TRH and endogenous corticosteroids in man

Recent studies suggest that submaximal plasma prolactin responses to TRH may reflect the effects of endogenous dopamine on prolactin release more accurately than basal plasma prolactin levels or maximal plasma prolactin responses to TRH. In the present study the plasma prolactin response to 12.5 micrograms i.v. TRH in 25 male subjects was significantly correlated with 24-hour urinary 17-ketogenic steroid excretion (= "total" 17-hydroxy corticosteroids). With regard to the basal plasma prolactin level or the prolactin response to 200 micrograms i.v. TRH, no such relation with corticosteroid excretion was detected. It is concluded that the plasma prolactin response to 12.5 micrograms i.v. TRH may provide a new, useful investigative tool with which to study corticosteroid-dopamine interactions and central dopamine activity in man.