The effects of TRH administration (400 microg, i.v.) on the release of prolactin were examined in 15 patients who met DSM-III-R criteria for panic disorder and 15 normal control subjects. Four hundred micrograms TRH was given via IV route. Blood samples were taken before TRH administration (baseline values) and at 15, 30 and 60 min. The results demonstrate that prolactin responses to TRH did not differ between panic disorder patients and normal control subjects. When only women were evaluated, the findings indicate that women with PD tend to show excessive prolactin responses to TRH. The findings are discussed in view of findings from earlier reports.