Impaired prolactin release in Huntington's chorea. Evidence for dopaminergic excess.

Eight individuals with Huntington's chorea had low basal and impaired human prolactin responses to both chlorpromazine and thyrotrophin-releasing hormone. These findings are compatible with enhanced hypothalamic dopaminergic activity in this disease. Two juvenile rigid patients with Huntington's chorea had excessive prolactin responses to chlorpromazine. Approximately half of the twenty-three potentially affected first-degree relatives of patients with Huntington's chorea had normal prolactin responses to chlorpromazine. However, twelve had significantly abnormal responses-seven in one direction, and five in the other. The predictive value of these findings in terms of presymptomatic diagnosis will be revealed by a longitudinal study. A biochemical method for the early recognition of the condition would have profound implications for genetic counselling.