Prolactin responses to provocative thyrotropin releasing hormone (TRH) stimulation were evaluated in 20 cirrhotic men with gynecomastia. Fifteen of these cirrhotic men had normal responses with a minimum doubling of the prolactin concentration above basal in response to TRH. Five had abnormal (autonomous) responses in that they failed to double their basal level or had a paradoxical decrease from basal in response to TRH. Moreover, these same five men failed to have a sleep-related increase in plasma prolactin. Three of them also failed to respond to chlorpromazine stimulation. Such abnormal responses are generally associated with the presence of a prolactin secreting pituitary tumor. Basal plasma levels of prolactin were measured in all 20 men studied. The five men who failed to respond to TRH had significantly greater basal prolactin concentrations (80.5 +/- 18.7 ng/ml) than did the 15 men who responded normally (33.7 +/- 4.3 ng/ml) (p less than 0.01), although all 20 had increased prolactin levels relative to that of controls (10.8 +/- 0.9 ng/ml) (both p less than 0.01).